+Syntax: +
+pair_style edip ++
Examples: +
+pair_style edip +pair_coeff * * Si.edip Si +
+Description: +
+The edip style computes a 3-body EDIP +potential for the energy E of a system of atoms as +
+
+where phi2 is a two-body term and phi3 is a three-body term. The +summations in the formula are over all neighbors J and K of atom I +within a cutoff distance = a. +Both terms depend on the local environment of atom I through its +effective coordination number defined by Z, which is unity for a +cutoff distance < c and gently goes to 0 at distance = a. +
+Only a single pair_coeff command is used with the edip style which +specifies a EDIP potential file with parameters for all +needed elements. These are mapped to LAMMPS atom types by specifying +N additional arguments after the filename in the pair_coeff command, +where N is the number of LAMMPS atom types: +
+As an example, imagine a file Si.edip has EDIP values for Si. +
+EDIP files in the potentials directory of the LAMMPS +distribution have a ".edip" suffix. Lines that are not blank or +comments (starting with #) define parameters for a triplet of +elements. The parameters in a single entry correspond to the two-body +and three-body coefficients in the formula above: +
+The A, B, beta, sigma parameters are used only for two-body interactions. +The eta, gamma, lambda, mu, Q0 and all u1 to u4 parameters are used only +for three-body interactions. The alpha and cutoffC parameters are used +for the coordination environment function only. +
+The EDIP potential file must contain entries for all the +elements listed in the pair_coeff command. It can also contain +entries for additional elements not being used in a particular +simulation; LAMMPS ignores those entries. +
+For a single-element simulation, only a single entry is required +(e.g. SiSiSi). For a two-element simulation, the file must contain 8 +entries (for SiSiSi, SiSiC, SiCSi, SiCC, CSiSi, CSiC, CCSi, CCC), that +specify EDIP parameters for all permutations of the two elements +interacting in three-body configurations. Thus for 3 elements, 27 +entries would be required, etc. +
+At the moment, only a single element parametrization is +implemented. However, the author is not aware of other +multi-element EDIP parametrizations. If you know any and +you are interest in that, please contact the author of +the EDIP package. +
+Mixing, shift, table, tail correction, restart, rRESPA info: +
+This pair style does not support the pair_modify +shift, table, and tail options. +
+This pair style does not write its information to binary restart +files, since it is stored in potential files. Thus, you +need to re-specify the pair_style and pair_coeff commands in an input +script that reads a restart file. +
+This pair style can only be used via the pair keyword of the +run_style respa command. It does not support the +inner, middle, outer keywords. +
+Restrictions: +
+This angle style can only be used if LAMMPS was built with the +USER-MISC package. See the Making LAMMPS +section for more info on packages. +
+This pair style requires the newton setting to be "on" +for pair interactions. +
+The EDIP potential files provided with LAMMPS (see the potentials directory) +are parameterized for metal units. +You can use the SW potential with any LAMMPS units, but you would need +to create your own EDIP potential file with coefficients listed in the +appropriate units if your simulation doesn't use "metal" units. +
+Related commands: +
+ +Default: none +
+(EDIP) J. F. Justo et al., Phys. Rev. B 58, 2539 (1998). +
+ diff --git a/doc/pair_edip.txt b/doc/pair_edip.txt new file mode 100644 index 0000000000..7087a9c259 --- /dev/null +++ b/doc/pair_edip.txt @@ -0,0 +1,137 @@ +"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 edip command :h3 + +[Syntax:] + +pair_style edip :pre + +[Examples:] + +pair_style edip +pair_coeff * * Si.edip Si + +[Description:] + +The {edip} style computes a 3-body "EDIP"_#EDIP +potential for the energy E of a system of atoms as + +:c,image(Eqs/pair_edip.jpg) + +where phi2 is a two-body term and phi3 is a three-body term. The +summations in the formula are over all neighbors J and K of atom I +within a cutoff distance = a. +Both terms depend on the local environment of atom I through its +effective coordination number defined by Z, which is unity for a +cutoff distance < c and gently goes to 0 at distance = a. + +Only a single pair_coeff command is used with the {edip} style which +specifies a EDIP potential file with parameters for all +needed elements. These are mapped to LAMMPS atom types by specifying +N additional arguments after the filename in the pair_coeff command, +where N is the number of LAMMPS atom types: + +filename +N element names = mapping of EDIP elements to atom types :ul + +As an example, imagine a file Si.edip has EDIP values for Si. + +EDIP files in the {potentials} directory of the LAMMPS +distribution have a ".edip" suffix. Lines that are not blank or +comments (starting with #) define parameters for a triplet of +elements. The parameters in a single entry correspond to the two-body +and three-body coefficients in the formula above: + +element 1 (the center atom in a 3-body interaction) +element 2 +element 3 +A (energy units) +B (distance units) +cutoffA (distance units) +cutoffC (distance units) +alpha +beta +eta +gamma (distance units) +lambda (energy units) +mu +tho +sigma (distance units) +Q0 +u1 +u2 +u3 +u4 :ul + +The A, B, beta, sigma parameters are used only for two-body interactions. +The eta, gamma, lambda, mu, Q0 and all u1 to u4 parameters are used only +for three-body interactions. The alpha and cutoffC parameters are used +for the coordination environment function only. + +The EDIP potential file must contain entries for all the +elements listed in the pair_coeff command. It can also contain +entries for additional elements not being used in a particular +simulation; LAMMPS ignores those entries. + +For a single-element simulation, only a single entry is required +(e.g. SiSiSi). For a two-element simulation, the file must contain 8 +entries (for SiSiSi, SiSiC, SiCSi, SiCC, CSiSi, CSiC, CCSi, CCC), that +specify EDIP parameters for all permutations of the two elements +interacting in three-body configurations. Thus for 3 elements, 27 +entries would be required, etc. + +At the moment, only a single element parametrization is +implemented. However, the author is not aware of other +multi-element EDIP parametrizations. If you know any and +you are interest in that, please contact the author of +the EDIP package. + +:line + +[Mixing, shift, table, tail correction, restart, rRESPA info]: + +This pair style does not support the "pair_modify"_pair_modify.html +shift, table, and tail options. + +This pair style does not write its information to "binary restart +files"_restart.html, since it is stored in potential files. Thus, you +need to re-specify the pair_style and pair_coeff commands in an input +script that reads a restart file. + +This pair style can only be used via the {pair} keyword of the +"run_style respa"_run_style.html command. It does not support the +{inner}, {middle}, {outer} keywords. + +:line + +[Restrictions:] + +This angle style can only be used if LAMMPS was built with the +USER-MISC package. See the "Making LAMMPS"_Section_start.html#start_3 +section for more info on packages. + +This pair style requires the "newton"_newton.html setting to be "on" +for pair interactions. + +The EDIP potential files provided with LAMMPS (see the potentials directory) +are parameterized for metal "units"_units.html. +You can use the SW potential with any LAMMPS units, but you would need +to create your own EDIP potential file with coefficients listed in the +appropriate units if your simulation doesn't use "metal" units. + +[Related commands:] + +"pair_coeff"_pair_coeff.html + +[Default:] none + +:line + +:link(EDIP) +[(EDIP)] J. F. Justo et al., Phys. Rev. B 58, 2539 (1998).