git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@252 f3b2605a-c512-4ea7-a41b-209d697bcdaa
This commit is contained in:
@ -326,8 +326,8 @@ description:
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<TR ALIGN="center"><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/charmm</A></TD><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/charmm/implicit</A></TD><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/long</A></TD><TD ><A HREF = "pair_style_class2.html">lj/class2</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/charmm</A></TD><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/charmm/implicit</A></TD><TD ><A HREF = "pair_style_charmm.html">lj/charmm/coul/long</A></TD><TD ><A HREF = "pair_style_class2.html">lj/class2</A></TD></TR>
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||||||
<TR ALIGN="center"><TD ><A HREF = "pair_style_class2.html">lj/class2/coul/cut</A></TD><TD ><A HREF = "pair_style_class2.html">lj/class2/coul/long</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/cut</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_class2.html">lj/class2/coul/cut</A></TD><TD ><A HREF = "pair_style_class2.html">lj/class2/coul/long</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/cut</A></TD></TR>
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||||||
<TR ALIGN="center"><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/debye</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/long</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/long/tip4p</A></TD><TD ><A HREF = "pair_style_lj_expand.html">lj/expand</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/debye</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/long</A></TD><TD ><A HREF = "pair_style_lj.html">lj/cut/coul/long/tip4p</A></TD><TD ><A HREF = "pair_style_lj_expand.html">lj/expand</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_lj_smooth.html">lj/smooth</A></TD><TD ><A HREF = "pair_style_morse.html">morse</A></TD><TD ><A HREF = "pair_style_soft.html">soft</A></TD><TD ><A HREF = "pair_style_sw.html">sw</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_lj_smooth.html">lj/smooth</A></TD><TD ><A HREF = "pair_style_meam.html">meam</A></TD><TD ><A HREF = "pair_style_morse.html">morse</A></TD><TD ><A HREF = "pair_style_soft.html">soft</A></TD></TR>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_table.html">table</A></TD><TD ><A HREF = "pair_style_tersoff.html">tersoff</A></TD><TD ><A HREF = "pair_style_yukawa.html">yukawa</A>
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<TR ALIGN="center"><TD ><A HREF = "pair_style_sw.html">sw</A></TD><TD ><A HREF = "pair_style_table.html">table</A></TD><TD ><A HREF = "pair_style_tersoff.html">tersoff</A></TD><TD ><A HREF = "pair_style_yukawa.html">yukawa</A>
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</TD></TR></TABLE></DIV>
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</TD></TR></TABLE></DIV>
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<P>Bond styles. See the <A HREF = "bond_style.html">bond_style</A> command for an
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<P>Bond styles. See the <A HREF = "bond_style.html">bond_style</A> command for an
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@ -433,6 +433,7 @@ description:
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|||||||
"lj/cut/coul/long/tip4p"_pair_style_lj.html,
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"lj/cut/coul/long/tip4p"_pair_style_lj.html,
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||||||
"lj/expand"_pair_style_lj_expand.html,
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"lj/expand"_pair_style_lj_expand.html,
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"lj/smooth"_pair_style_lj_smooth.html,
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"lj/smooth"_pair_style_lj_smooth.html,
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|
"meam"_pair_style_meam.html,
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"morse"_pair_style_morse.html,
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"morse"_pair_style_morse.html,
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"soft"_pair_style_soft.html,
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"soft"_pair_style_soft.html,
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"sw"_pair_style_sw.html,
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"sw"_pair_style_sw.html,
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@ -110,6 +110,7 @@ the pair_style command, and coefficients specified by the associated
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<LI><A HREF = "pair_style_lj.html">pair_style lj/cut/coul/long/tip4p</A> - LJ with long-range Coulomb for TIP4P water
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<LI><A HREF = "pair_style_lj.html">pair_style lj/cut/coul/long/tip4p</A> - LJ with long-range Coulomb for TIP4P water
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||||||
<LI><A HREF = "pair_style_lj_expand.html">pair_style lj/expand</A> - Lennard-Jones for variable size particles
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<LI><A HREF = "pair_style_lj_expand.html">pair_style lj/expand</A> - Lennard-Jones for variable size particles
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<LI><A HREF = "pair_style_lj_smooth.html">pair_style lj/smooth</A> - smoothed Lennard-Jones potential
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<LI><A HREF = "pair_style_lj_smooth.html">pair_style lj/smooth</A> - smoothed Lennard-Jones potential
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||||||
|
<LI><A HREF = "pair_style_meam.html">pair_style meam</A> - modified embedded atom method (MEAM)
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||||||
<LI><A HREF = "pair_style_morse.html">pair_style morse</A> - Morse potential
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<LI><A HREF = "pair_style_morse.html">pair_style morse</A> - Morse potential
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<LI><A HREF = "pair_style_soft.html">pair_style soft</A> - Soft (cosine) potential
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<LI><A HREF = "pair_style_soft.html">pair_style soft</A> - Soft (cosine) potential
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<LI><A HREF = "pair_style_sw.html">pair_style sw</A> - Stillinger-Weber 3-body potential
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<LI><A HREF = "pair_style_sw.html">pair_style sw</A> - Stillinger-Weber 3-body potential
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@ -107,6 +107,7 @@ the pair_style command, and coefficients specified by the associated
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"pair_style lj/cut/coul/long/tip4p"_pair_style_lj.html - LJ with long-range Coulomb for TIP4P water
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"pair_style lj/cut/coul/long/tip4p"_pair_style_lj.html - LJ with long-range Coulomb for TIP4P water
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||||||
"pair_style lj/expand"_pair_style_lj_expand.html - Lennard-Jones for variable size particles
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"pair_style lj/expand"_pair_style_lj_expand.html - Lennard-Jones for variable size particles
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"pair_style lj/smooth"_pair_style_lj_smooth.html - smoothed Lennard-Jones potential
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"pair_style lj/smooth"_pair_style_lj_smooth.html - smoothed Lennard-Jones potential
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||||||
|
"pair_style meam"_pair_style_meam.html - modified embedded atom method (MEAM)
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||||||
"pair_style morse"_pair_style_morse.html - Morse potential
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"pair_style morse"_pair_style_morse.html - Morse potential
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"pair_style soft"_pair_style_soft.html - Soft (cosine) potential
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"pair_style soft"_pair_style_soft.html - Soft (cosine) potential
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"pair_style sw"_pair_style_sw.html - Stillinger-Weber 3-body potential
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"pair_style sw"_pair_style_sw.html - Stillinger-Weber 3-body potential
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@ -29,6 +29,7 @@
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<LI><I>lj/cut</I> or <I>lj/cut/coul/cut</I> or <I>lj/cut/coul/debye</I> or <I>lj/cut/coul/long</I> or <I>lj/cut/coul/long/tip4p</I>
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<LI><I>lj/cut</I> or <I>lj/cut/coul/cut</I> or <I>lj/cut/coul/debye</I> or <I>lj/cut/coul/long</I> or <I>lj/cut/coul/long/tip4p</I>
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||||||
<LI><I>lj/expand</I>
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<LI><I>lj/expand</I>
|
||||||
<LI><I>lj/smooth</I>
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<LI><I>lj/smooth</I>
|
||||||
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<LI><I>meam</I>
|
||||||
<LI><I>morse</I>
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<LI><I>morse</I>
|
||||||
<LI><I>soft</I>
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<LI><I>soft</I>
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||||||
<LI><I>sw</I>
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<LI><I>sw</I>
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@ -126,6 +127,7 @@ the pair_style command, and coefficients specified by the associated
|
|||||||
<LI><A HREF = "pair_style_lj.html">pair_style lj/cut/coul/long/tip4p</A> - LJ with long-range Coulomb for TIP4P water
|
<LI><A HREF = "pair_style_lj.html">pair_style lj/cut/coul/long/tip4p</A> - LJ with long-range Coulomb for TIP4P water
|
||||||
<LI><A HREF = "pair_style_lj_expand.html">pair_style lj/expand</A> - Lennard-Jones for variable size particles
|
<LI><A HREF = "pair_style_lj_expand.html">pair_style lj/expand</A> - Lennard-Jones for variable size particles
|
||||||
<LI><A HREF = "pair_style_lj_smooth.html">pair_style lj/smooth</A> - smoothed Lennard-Jones potential
|
<LI><A HREF = "pair_style_lj_smooth.html">pair_style lj/smooth</A> - smoothed Lennard-Jones potential
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||||||
|
<LI><A HREF = "pair_style_meam.html">pair_style meam</A> - modified embedded atom method (MEAM)
|
||||||
<LI><A HREF = "pair_style_morse.html">pair_style morse</A> - Morse potential
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<LI><A HREF = "pair_style_morse.html">pair_style morse</A> - Morse potential
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||||||
<LI><A HREF = "pair_style_soft.html">pair_style soft</A> - Soft (cosine) potential
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<LI><A HREF = "pair_style_soft.html">pair_style soft</A> - Soft (cosine) potential
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||||||
<LI><A HREF = "pair_style_sw.html">pair_style sw</A> - Stillinger-Weber 3-body potential
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<LI><A HREF = "pair_style_sw.html">pair_style sw</A> - Stillinger-Weber 3-body potential
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||||||
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@ -26,6 +26,7 @@ style = one of the following :ulb,l
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{lj/cut} or {lj/cut/coul/cut} or {lj/cut/coul/debye} or {lj/cut/coul/long} or {lj/cut/coul/long/tip4p}
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{lj/cut} or {lj/cut/coul/cut} or {lj/cut/coul/debye} or {lj/cut/coul/long} or {lj/cut/coul/long/tip4p}
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||||||
{lj/expand}
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{lj/expand}
|
||||||
{lj/smooth}
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{lj/smooth}
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||||||
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{meam}
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{morse}
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{morse}
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{soft}
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{soft}
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{sw}
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{sw}
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@ -123,6 +124,7 @@ the pair_style command, and coefficients specified by the associated
|
|||||||
"pair_style lj/cut/coul/long/tip4p"_pair_style_lj.html - LJ with long-range Coulomb for TIP4P water
|
"pair_style lj/cut/coul/long/tip4p"_pair_style_lj.html - LJ with long-range Coulomb for TIP4P water
|
||||||
"pair_style lj/expand"_pair_style_lj_expand.html - Lennard-Jones for variable size particles
|
"pair_style lj/expand"_pair_style_lj_expand.html - Lennard-Jones for variable size particles
|
||||||
"pair_style lj/smooth"_pair_style_lj_smooth.html - smoothed Lennard-Jones potential
|
"pair_style lj/smooth"_pair_style_lj_smooth.html - smoothed Lennard-Jones potential
|
||||||
|
"pair_style meam"_pair_style_meam.html - modified embedded atom method (MEAM)
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||||||
"pair_style morse"_pair_style_morse.html - Morse potential
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"pair_style morse"_pair_style_morse.html - Morse potential
|
||||||
"pair_style soft"_pair_style_soft.html - Soft (cosine) potential
|
"pair_style soft"_pair_style_soft.html - Soft (cosine) potential
|
||||||
"pair_style sw"_pair_style_sw.html - Stillinger-Weber 3-body potential
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"pair_style sw"_pair_style_sw.html - Stillinger-Weber 3-body potential
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@ -72,4 +72,10 @@ pairs must be specified explicitly.
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</P>
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</P>
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<P><B>Default:</B> none
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<P><B>Default:</B> none
|
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</P>
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</P>
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<HR>
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||||||
|
|
||||||
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<A NAME = "Groot"></A>
|
||||||
|
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||||||
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<P><B>(Groot)</B> Groot and Warren, J Chem Phys, 107, 4423-35 (1997).
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||||||
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</P>
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||||||
</HTML>
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</HTML>
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@ -68,3 +68,8 @@ pairs must be specified explicitly.
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"pair_coeff"_pair_coeff.html
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"pair_coeff"_pair_coeff.html
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[Default:] none
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[Default:] none
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||||||
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:line
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:link(Groot)
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[(Groot)] Groot and Warren, J Chem Phys, 107, 4423-35 (1997).
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@ -51,11 +51,11 @@ within the cutoff distance.
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<P>The cutoff distance and the tabulated values of the functionals F,
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<P>The cutoff distance and the tabulated values of the functionals F,
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rho, and phi are listed in one or more files which are specified by
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rho, and phi are listed in one or more files which are specified by
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the <A HREF = "pair_coeff.html">pair_coeff</A> command. These are ASCII text files
|
the <A HREF = "pair_coeff.html">pair_coeff</A> command. These are ASCII text files
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||||||
in a DYNAMO-style format which is described in the documentation for
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in a DYNAMO-style format which is described below. DYNAMO is a serial
|
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the <A HREF = "pair_coeff.html">pair_coeff</A> command. DYNAMO is a serial MD code
|
MD code. Several DYNAMO potential files for different metals are
|
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Several DYNAMO potential files for different metals are included in
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included in the "potentials" directory of the LAMMPS distribution.
|
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the "potentials" directory of the LAMMPS distribution. All of these
|
All of these are parameterized in terms of LAMMPS <A HREF = "units.html">metal
|
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are paremeterized in terms of LAMMPS <A HREF = "units.html">metal units</A>.
|
units</A>.
|
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</P>
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</P>
|
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<P>IMPORTANT NOTE: The <I>eam</I> style reads single-element EAM potentials in
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<P>IMPORTANT NOTE: The <I>eam</I> style reads single-element EAM potentials in
|
||||||
the DYNAMO <I>funcfl</I> format. Either single element or alloy systems
|
the DYNAMO <I>funcfl</I> format. Either single element or alloy systems
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@ -46,11 +46,11 @@ within the cutoff distance.
|
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The cutoff distance and the tabulated values of the functionals F,
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The cutoff distance and the tabulated values of the functionals F,
|
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rho, and phi are listed in one or more files which are specified by
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rho, and phi are listed in one or more files which are specified by
|
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the "pair_coeff"_pair_coeff.html command. These are ASCII text files
|
the "pair_coeff"_pair_coeff.html command. These are ASCII text files
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||||||
in a DYNAMO-style format which is described in the documentation for
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in a DYNAMO-style format which is described below. DYNAMO is a serial
|
||||||
the "pair_coeff"_pair_coeff.html command. DYNAMO is a serial MD code
|
MD code. Several DYNAMO potential files for different metals are
|
||||||
Several DYNAMO potential files for different metals are included in
|
included in the "potentials" directory of the LAMMPS distribution.
|
||||||
the "potentials" directory of the LAMMPS distribution. All of these
|
All of these are parameterized in terms of LAMMPS "metal
|
||||||
are paremeterized in terms of LAMMPS "metal units"_units.html.
|
units"_units.html.
|
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|
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IMPORTANT NOTE: The {eam} style reads single-element EAM potentials in
|
IMPORTANT NOTE: The {eam} style reads single-element EAM potentials in
|
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the DYNAMO {funcfl} format. Either single element or alloy systems
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the DYNAMO {funcfl} format. Either single element or alloy systems
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207
doc/pair_style_meam.html
Normal file
207
doc/pair_style_meam.html
Normal file
@ -0,0 +1,207 @@
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<HTML>
|
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<CENTER><A HREF = "http://lammps.sandia.gov">LAMMPS WWW Site</A> - <A HREF = "Manual.html">LAMMPS Documentation</A> - <A HREF = "Section_commands.html#comm">LAMMPS Commands</A>
|
||||||
|
</CENTER>
|
||||||
|
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||||||
|
|
||||||
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|
||||||
|
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||||||
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||||||
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<HR>
|
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|
|
||||||
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<H3>pair_style meam command
|
||||||
|
</H3>
|
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|
<P><B>Syntax:</B>
|
||||||
|
</P>
|
||||||
|
<PRE>pair_style mean
|
||||||
|
</PRE>
|
||||||
|
<P><B>Examples:</B>
|
||||||
|
</P>
|
||||||
|
<PRE>pair_style meam
|
||||||
|
pair_coeff * * ../potentials/library.meam Si ../potentials/si.meam Si
|
||||||
|
pair_coeff * * ../potentials/library.meam Ni Al NULL Ni Al Ni Ni
|
||||||
|
</PRE>
|
||||||
|
<P><B>Description:</B>
|
||||||
|
</P>
|
||||||
|
<P>Style <I>meam</I> computes pairwise interactions for a variety of materials
|
||||||
|
using modified embedded-atom method (MEAM) potentials
|
||||||
|
<A HREF = "#Baskes">(Baskes)</A>. Conceptually, it is an extension to the original
|
||||||
|
<A HREF = "pair_style_eam.html">EAM potentials</A> which adds angular forces. It is
|
||||||
|
thus suitable for modeling metals and alloys with fcc, bcc, hcp and
|
||||||
|
diamond cubic structures, as well as covalently bonded materials like
|
||||||
|
silicon and carbon.
|
||||||
|
</P>
|
||||||
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<P>In the MEAM formulation, the total energy E of a system of atoms is
|
||||||
|
given by:
|
||||||
|
</P>
|
||||||
|
<CENTER><IMG SRC = "Eqs/pair_meam.jpg">
|
||||||
|
</CENTER>
|
||||||
|
<P>where F is the embedding energy which is a function of the atomic
|
||||||
|
electron density rho, and phi is a pair potential interaction. The
|
||||||
|
pair interaction is summed over all neighbors J of atom I within the
|
||||||
|
cutoff distance. As with EAM, the multi-body nature of the MEAM
|
||||||
|
potential is a result of the embedding energy term. Details of the
|
||||||
|
computation of the embedding and pair energies, as implemented in
|
||||||
|
LAMMPS, are given in <A HREF = "#Gullet">(Gullet)</A> and references therein.
|
||||||
|
</P>
|
||||||
|
<P>The various parameters in the MEAM formulas are listed in two files
|
||||||
|
which are specified by the <A HREF = "pair_coeff.html">pair_coeff</A> command.
|
||||||
|
These are ASCII text files in a format consistent with other MD codes
|
||||||
|
that implement MEAM potentials, such as the serial DYNAMO code and
|
||||||
|
Warp. Several MEAM potential files with parameters for different
|
||||||
|
materials are included in the "potentials" directory of the LAMMPS
|
||||||
|
distribution with a ",meam" suffix. All of these are parameterized in
|
||||||
|
terms of LAMMPS <A HREF = "units.html">metal units</A>.
|
||||||
|
</P>
|
||||||
|
<P>Note that unlike for other potentials, cutoffs for MEAM potentials are
|
||||||
|
not set in the pair_style or pair_coeff command; they are specified in
|
||||||
|
the MEAM potential files themselves.
|
||||||
|
</P>
|
||||||
|
<P>Only a single pair_coeff command is used with the <I>meam</I> style which
|
||||||
|
specifies two MEAM files and the element(s) to extract information
|
||||||
|
for. The MEAM elements are mapped to LAMMPS atom types by specifying
|
||||||
|
N additional arguments after the 2nd filename in the pair_coeff
|
||||||
|
command, where N is the number of LAMMPS atom types:
|
||||||
|
</P>
|
||||||
|
<UL><LI>MEAM library file
|
||||||
|
<LI>Elem1, Elem2, ...
|
||||||
|
<LI>MEAM parameter file
|
||||||
|
<LI>N element names = mapping of MEAM elements to atom types
|
||||||
|
</UL>
|
||||||
|
<P>As an example, the potentials/library.meam file has generic MEAM
|
||||||
|
settings for a variety of elements. The potentials/sic.meam file has
|
||||||
|
specific parameter settings for a Si and C alloy system. If your
|
||||||
|
LAMMPS simulation has 4 atoms types and you want the 1st 3 to be Si,
|
||||||
|
and the 4th to be C, you would use the following pair_coeff command:
|
||||||
|
</P>
|
||||||
|
<PRE>pair_coeff * * library.meam Si C sic.meam Si Si Si C
|
||||||
|
</PRE>
|
||||||
|
<P>The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
|
||||||
|
The two filenames are for the library and parameter file respectively.
|
||||||
|
The Si and C arguments (between the file names) are the two elements
|
||||||
|
for which info will be extracted from the library file. The first
|
||||||
|
three trailing Si arguments map LAMMPS atom types 1,2,3 to the MEAM Si
|
||||||
|
element. The final C argument maps LAMMPS atom type 4 to the MEAM C
|
||||||
|
element.
|
||||||
|
</P>
|
||||||
|
<P>If the 2nd filename is specified as NULL, no parameter file is read,
|
||||||
|
which simply means the generic parameters in the library file are
|
||||||
|
used. Use of the NULL specification for the parameter file is
|
||||||
|
discouraged for systems with more than a single element type
|
||||||
|
(e.g. alloys), since the parameter file is expected to set element
|
||||||
|
interaction terms that are not captured by the information in the
|
||||||
|
library file.
|
||||||
|
</P>
|
||||||
|
<P>If a mapping value is specified as NULL, the mapping is not performed.
|
||||||
|
This can be used when a <I>meam</I> potential is used as part of the
|
||||||
|
<I>hybrid</I> pair style. The NULL values are placeholders for atom types
|
||||||
|
that will be used with other potentials.
|
||||||
|
</P>
|
||||||
|
<P>The MEAM library file provided with LAMMPS has the name
|
||||||
|
potentials/library.meam. It is the "meamf" file used by other MD
|
||||||
|
codes. Aside from blank and comment lines (start with #) which can
|
||||||
|
appear anywhere, it is formatted as a series of entries, each of which
|
||||||
|
has 19 parameters and can span multiple lines:
|
||||||
|
</P>
|
||||||
|
<P>elt, lat, z, ielement, atwt, alpha, b0, b1, b2, b3, alat, esub, asub,
|
||||||
|
t0, t1, t2, t3, rozero, ibar
|
||||||
|
</P>
|
||||||
|
<P>The "elt" and "lat" parameters are text strings, such as elt = Si or
|
||||||
|
Cu and lat = dia or fcc. Because the library file is used by Fortran
|
||||||
|
MD codes, these strings may be enclosed in single quotes, but this is
|
||||||
|
not required. The other numeric parameters match values in the
|
||||||
|
formulas above. The value of the "elt" string is what is used in the
|
||||||
|
pair_coeff command to identify which settings from the library file
|
||||||
|
you wish to read in. There can be multiple entries in the library
|
||||||
|
file with the same "elt" value; LAMMPS reads the 1st matching entry it
|
||||||
|
finds and ignores the rest.
|
||||||
|
</P>
|
||||||
|
<P>If used, the MEAM parameter file contains settings that override or
|
||||||
|
complement the library file settings. Examples of such parameter
|
||||||
|
files are in the potentials directory with a ".meam" suffix. Their
|
||||||
|
format is the same as is read by other Fortran MD codes. Aside from
|
||||||
|
blank and comment lines (start with #) which can appear anywhere, each
|
||||||
|
line has one of the following forms. Each line can also have a
|
||||||
|
trailing comment (starting with #) which is ignored.
|
||||||
|
</P>
|
||||||
|
<PRE>keyword = value
|
||||||
|
keyword(I) = value
|
||||||
|
keyword(I,J) = value
|
||||||
|
keyword(I,J,K) = value
|
||||||
|
</PRE>
|
||||||
|
<P>The recognized keywords are as follows:
|
||||||
|
</P>
|
||||||
|
<P>Ec, alpha, rho0, delta, lattce, attrac, repuls, nn2, Cmin, Cmax, rc, delr,
|
||||||
|
augt1, gsmooth_factor, re
|
||||||
|
</P>
|
||||||
|
<P>where
|
||||||
|
</P>
|
||||||
|
<PRE>rc = cutoff radius for cutoff function; default = 4.0
|
||||||
|
delr = length of smoothing distance for cutoff function; default = 0.1
|
||||||
|
rho0(I) = relative density for element I (overwrites value
|
||||||
|
read from meamf file)
|
||||||
|
Ec(I,J) = cohesive energy of reference structure for I-J mixture
|
||||||
|
delta(I,J) = heat of formation for I-J alloy; if Ec_IJ is input as
|
||||||
|
zero, then WARP sets Ec_IJ = (Ec_II + Ec_JJ)/2 - delta_IJ
|
||||||
|
alpha(I,J) = alpha parameter for pair potential between I and J (can
|
||||||
|
be computed from bulk modulus of reference structure
|
||||||
|
re(I,J) = equilibrium distance between I and J in the reference
|
||||||
|
structure
|
||||||
|
Cmax(I,J,K) = Cmax screening parameter when I-J pair is screened
|
||||||
|
by K (I<=J); default = 2.8
|
||||||
|
Cmin(I,J,K) = Cmin screening parameter when I-J pair is screened
|
||||||
|
by K (I<=J); default = 2.0
|
||||||
|
lattce(I,J) = lattice structure of I-J reference structure:
|
||||||
|
dia = diamond (interlaced fcc for alloy)
|
||||||
|
fcc = face centered cubic
|
||||||
|
bcc = body centered cubic
|
||||||
|
dim = dimer
|
||||||
|
B1 = rock salt (NaCl structure)
|
||||||
|
gsmooth_factor = factor determining the length of the G-function smoothing
|
||||||
|
region; only significant for ibar=0 or ibar=4.
|
||||||
|
99.0 = short smoothing region, sharp step
|
||||||
|
0.5 = long smoothing region, smooth step
|
||||||
|
default = 99.0
|
||||||
|
augt1 = integer flag for whether to augment t1 parameter by
|
||||||
|
3/5*t3 to account for old vs. new meam formulations;
|
||||||
|
0 = don't augment t1
|
||||||
|
1 = augment t1
|
||||||
|
default = 1
|
||||||
|
</PRE>
|
||||||
|
<P>Each keyword represents a quantity which is either a scalar, vector,
|
||||||
|
2d array, or 3d array and must be specified with the correct
|
||||||
|
corresponding array syntax. The indices I,J,K each run from 1 to N
|
||||||
|
where N is the number of MEAM elements being used.
|
||||||
|
</P>
|
||||||
|
<P>Thus these lines
|
||||||
|
</P>
|
||||||
|
<PRE>rho0(2) = 2.25
|
||||||
|
alpha(1,2) = 4.37
|
||||||
|
</PRE>
|
||||||
|
<P>mean set rho0 for the 2nd element to the value 2.25 and set alpha for
|
||||||
|
the alloy interaction between elements 1 and 2 to 4.37.
|
||||||
|
</P>
|
||||||
|
<HR>
|
||||||
|
|
||||||
|
<P><B>Restrictions:</B> none
|
||||||
|
</P>
|
||||||
|
<P><B>Related commands:</B>
|
||||||
|
</P>
|
||||||
|
<P><A HREF = "pair_coeff.html">pair_coeff</A>, <A HREF = "pair_style_eam.html">pair_style eam</A>
|
||||||
|
</P>
|
||||||
|
<P><B>Default:</B> none
|
||||||
|
</P>
|
||||||
|
<HR>
|
||||||
|
|
||||||
|
<A NAME = "Baskes"></A>
|
||||||
|
|
||||||
|
<P><B>(Baskes)</B> Baskes, Phys Rev B, 46, 2727-2742 (1992).
|
||||||
|
</P>
|
||||||
|
<A NAME = "Gullet"></A>
|
||||||
|
|
||||||
|
<P><B>(Gullet)</B> Gullet, Wagner, Slepoy, SANDIA Report 2003-8782 (2003).
|
||||||
|
This report may be accessed on-line via <A HREF = "http://www.prod.sandia.gov/cgi-bin/techlib/access-control.pl/2003/038782.pdf">this link</A>.
|
||||||
|
</P>
|
||||||
|
|
||||||
|
|
||||||
|
</HTML>
|
||||||
200
doc/pair_style_meam.txt
Normal file
200
doc/pair_style_meam.txt
Normal file
@ -0,0 +1,200 @@
|
|||||||
|
"LAMMPS WWW Site"_lws - "LAMMPS Documentation"_ld - "LAMMPS Commands"_lc :c
|
||||||
|
|
||||||
|
:link(lws,http://lammps.sandia.gov)
|
||||||
|
:link(ld,Manual.html)
|
||||||
|
:link(lc,Section_commands.html#comm)
|
||||||
|
|
||||||
|
:line
|
||||||
|
|
||||||
|
pair_style meam command :h3
|
||||||
|
|
||||||
|
[Syntax:]
|
||||||
|
|
||||||
|
pair_style mean :pre
|
||||||
|
|
||||||
|
[Examples:]
|
||||||
|
|
||||||
|
pair_style meam
|
||||||
|
pair_coeff * * ../potentials/library.meam Si ../potentials/si.meam Si
|
||||||
|
pair_coeff * * ../potentials/library.meam Ni Al NULL Ni Al Ni Ni :pre
|
||||||
|
|
||||||
|
[Description:]
|
||||||
|
|
||||||
|
Style {meam} computes pairwise interactions for a variety of materials
|
||||||
|
using modified embedded-atom method (MEAM) potentials
|
||||||
|
"(Baskes)"_#Baskes. Conceptually, it is an extension to the original
|
||||||
|
"EAM potentials"_pair_style_eam.html which adds angular forces. It is
|
||||||
|
thus suitable for modeling metals and alloys with fcc, bcc, hcp and
|
||||||
|
diamond cubic structures, as well as covalently bonded materials like
|
||||||
|
silicon and carbon.
|
||||||
|
|
||||||
|
In the MEAM formulation, the total energy E of a system of atoms is
|
||||||
|
given by:
|
||||||
|
|
||||||
|
:c,image(Eqs/pair_meam.jpg)
|
||||||
|
|
||||||
|
where F is the embedding energy which is a function of the atomic
|
||||||
|
electron density rho, and phi is a pair potential interaction. The
|
||||||
|
pair interaction is summed over all neighbors J of atom I within the
|
||||||
|
cutoff distance. As with EAM, the multi-body nature of the MEAM
|
||||||
|
potential is a result of the embedding energy term. Details of the
|
||||||
|
computation of the embedding and pair energies, as implemented in
|
||||||
|
LAMMPS, are given in "(Gullet)"_#Gullet and references therein.
|
||||||
|
|
||||||
|
The various parameters in the MEAM formulas are listed in two files
|
||||||
|
which are specified by the "pair_coeff"_pair_coeff.html command.
|
||||||
|
These are ASCII text files in a format consistent with other MD codes
|
||||||
|
that implement MEAM potentials, such as the serial DYNAMO code and
|
||||||
|
Warp. Several MEAM potential files with parameters for different
|
||||||
|
materials are included in the "potentials" directory of the LAMMPS
|
||||||
|
distribution with a ",meam" suffix. All of these are parameterized in
|
||||||
|
terms of LAMMPS "metal units"_units.html.
|
||||||
|
|
||||||
|
Note that unlike for other potentials, cutoffs for MEAM potentials are
|
||||||
|
not set in the pair_style or pair_coeff command; they are specified in
|
||||||
|
the MEAM potential files themselves.
|
||||||
|
|
||||||
|
Only a single pair_coeff command is used with the {meam} style which
|
||||||
|
specifies two MEAM files and the element(s) to extract information
|
||||||
|
for. The MEAM elements are mapped to LAMMPS atom types by specifying
|
||||||
|
N additional arguments after the 2nd filename in the pair_coeff
|
||||||
|
command, where N is the number of LAMMPS atom types:
|
||||||
|
|
||||||
|
MEAM library file
|
||||||
|
Elem1, Elem2, ...
|
||||||
|
MEAM parameter file
|
||||||
|
N element names = mapping of MEAM elements to atom types :ul
|
||||||
|
|
||||||
|
As an example, the potentials/library.meam file has generic MEAM
|
||||||
|
settings for a variety of elements. The potentials/sic.meam file has
|
||||||
|
specific parameter settings for a Si and C alloy system. If your
|
||||||
|
LAMMPS simulation has 4 atoms types and you want the 1st 3 to be Si,
|
||||||
|
and the 4th to be C, you would use the following pair_coeff command:
|
||||||
|
|
||||||
|
pair_coeff * * library.meam Si C sic.meam Si Si Si C :pre
|
||||||
|
|
||||||
|
The 1st 2 arguments must be * * so as to span all LAMMPS atom types.
|
||||||
|
The two filenames are for the library and parameter file respectively.
|
||||||
|
The Si and C arguments (between the file names) are the two elements
|
||||||
|
for which info will be extracted from the library file. The first
|
||||||
|
three trailing Si arguments map LAMMPS atom types 1,2,3 to the MEAM Si
|
||||||
|
element. The final C argument maps LAMMPS atom type 4 to the MEAM C
|
||||||
|
element.
|
||||||
|
|
||||||
|
If the 2nd filename is specified as NULL, no parameter file is read,
|
||||||
|
which simply means the generic parameters in the library file are
|
||||||
|
used. Use of the NULL specification for the parameter file is
|
||||||
|
discouraged for systems with more than a single element type
|
||||||
|
(e.g. alloys), since the parameter file is expected to set element
|
||||||
|
interaction terms that are not captured by the information in the
|
||||||
|
library file.
|
||||||
|
|
||||||
|
If a mapping value is specified as NULL, the mapping is not performed.
|
||||||
|
This can be used when a {meam} potential is used as part of the
|
||||||
|
{hybrid} pair style. The NULL values are placeholders for atom types
|
||||||
|
that will be used with other potentials.
|
||||||
|
|
||||||
|
The MEAM library file provided with LAMMPS has the name
|
||||||
|
potentials/library.meam. It is the "meamf" file used by other MD
|
||||||
|
codes. Aside from blank and comment lines (start with #) which can
|
||||||
|
appear anywhere, it is formatted as a series of entries, each of which
|
||||||
|
has 19 parameters and can span multiple lines:
|
||||||
|
|
||||||
|
elt, lat, z, ielement, atwt, alpha, b0, b1, b2, b3, alat, esub, asub,
|
||||||
|
t0, t1, t2, t3, rozero, ibar
|
||||||
|
|
||||||
|
The "elt" and "lat" parameters are text strings, such as elt = Si or
|
||||||
|
Cu and lat = dia or fcc. Because the library file is used by Fortran
|
||||||
|
MD codes, these strings may be enclosed in single quotes, but this is
|
||||||
|
not required. The other numeric parameters match values in the
|
||||||
|
formulas above. The value of the "elt" string is what is used in the
|
||||||
|
pair_coeff command to identify which settings from the library file
|
||||||
|
you wish to read in. There can be multiple entries in the library
|
||||||
|
file with the same "elt" value; LAMMPS reads the 1st matching entry it
|
||||||
|
finds and ignores the rest.
|
||||||
|
|
||||||
|
If used, the MEAM parameter file contains settings that override or
|
||||||
|
complement the library file settings. Examples of such parameter
|
||||||
|
files are in the potentials directory with a ".meam" suffix. Their
|
||||||
|
format is the same as is read by other Fortran MD codes. Aside from
|
||||||
|
blank and comment lines (start with #) which can appear anywhere, each
|
||||||
|
line has one of the following forms. Each line can also have a
|
||||||
|
trailing comment (starting with #) which is ignored.
|
||||||
|
|
||||||
|
keyword = value
|
||||||
|
keyword(I) = value
|
||||||
|
keyword(I,J) = value
|
||||||
|
keyword(I,J,K) = value :pre
|
||||||
|
|
||||||
|
The recognized keywords are as follows:
|
||||||
|
|
||||||
|
Ec, alpha, rho0, delta, lattce, attrac, repuls, nn2, Cmin, Cmax, rc, delr,
|
||||||
|
augt1, gsmooth_factor, re
|
||||||
|
|
||||||
|
where
|
||||||
|
|
||||||
|
rc = cutoff radius for cutoff function; default = 4.0
|
||||||
|
delr = length of smoothing distance for cutoff function; default = 0.1
|
||||||
|
rho0(I) = relative density for element I (overwrites value
|
||||||
|
read from meamf file)
|
||||||
|
Ec(I,J) = cohesive energy of reference structure for I-J mixture
|
||||||
|
delta(I,J) = heat of formation for I-J alloy; if Ec_IJ is input as
|
||||||
|
zero, then WARP sets Ec_IJ = (Ec_II + Ec_JJ)/2 - delta_IJ
|
||||||
|
alpha(I,J) = alpha parameter for pair potential between I and J (can
|
||||||
|
be computed from bulk modulus of reference structure
|
||||||
|
re(I,J) = equilibrium distance between I and J in the reference
|
||||||
|
structure
|
||||||
|
Cmax(I,J,K) = Cmax screening parameter when I-J pair is screened
|
||||||
|
by K (I<=J); default = 2.8
|
||||||
|
Cmin(I,J,K) = Cmin screening parameter when I-J pair is screened
|
||||||
|
by K (I<=J); default = 2.0
|
||||||
|
lattce(I,J) = lattice structure of I-J reference structure:
|
||||||
|
dia = diamond (interlaced fcc for alloy)
|
||||||
|
fcc = face centered cubic
|
||||||
|
bcc = body centered cubic
|
||||||
|
dim = dimer
|
||||||
|
B1 = rock salt (NaCl structure)
|
||||||
|
gsmooth_factor = factor determining the length of the G-function smoothing
|
||||||
|
region; only significant for ibar=0 or ibar=4.
|
||||||
|
99.0 = short smoothing region, sharp step
|
||||||
|
0.5 = long smoothing region, smooth step
|
||||||
|
default = 99.0
|
||||||
|
augt1 = integer flag for whether to augment t1 parameter by
|
||||||
|
3/5*t3 to account for old vs. new meam formulations;
|
||||||
|
0 = don't augment t1
|
||||||
|
1 = augment t1
|
||||||
|
default = 1 :pre
|
||||||
|
|
||||||
|
Each keyword represents a quantity which is either a scalar, vector,
|
||||||
|
2d array, or 3d array and must be specified with the correct
|
||||||
|
corresponding array syntax. The indices I,J,K each run from 1 to N
|
||||||
|
where N is the number of MEAM elements being used.
|
||||||
|
|
||||||
|
Thus these lines
|
||||||
|
|
||||||
|
rho0(2) = 2.25
|
||||||
|
alpha(1,2) = 4.37 :pre
|
||||||
|
|
||||||
|
mean set rho0 for the 2nd element to the value 2.25 and set alpha for
|
||||||
|
the alloy interaction between elements 1 and 2 to 4.37.
|
||||||
|
|
||||||
|
:line
|
||||||
|
|
||||||
|
[Restrictions:] none
|
||||||
|
|
||||||
|
[Related commands:]
|
||||||
|
|
||||||
|
"pair_coeff"_pair_coeff.html, "pair_style eam"_pair_style_eam.html
|
||||||
|
|
||||||
|
[Default:] none
|
||||||
|
|
||||||
|
:line
|
||||||
|
|
||||||
|
:link(Baskes)
|
||||||
|
[(Baskes)] Baskes, Phys Rev B, 46, 2727-2742 (1992).
|
||||||
|
|
||||||
|
:link(Gullet)
|
||||||
|
[(Gullet)] Gullet, Wagner, Slepoy, SANDIA Report 2003-8782 (2003).
|
||||||
|
This report may be accessed on-line via "this link"_sandreport.
|
||||||
|
|
||||||
|
:link(sandreport,http://www.prod.sandia.gov/cgi-bin/techlib/access-control.pl/2003/038782.pdf)
|
||||||
Reference in New Issue
Block a user