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git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@7690 f3b2605a-c512-4ea7-a41b-209d697bcdaa

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@ -770,19 +770,29 @@ where lx = xhi-xlo, and similarly in the y and z dimensions. The 6
parameters, as well as lx,ly,lz, can be output via the <A HREF = "thermo_style.html">thermo_style
custom</A> command.
</P>
<P>LAMMPS also allows simulations to be perfored in non-orthogonal
simulation boxes shaped as a parallelepiped with triclinic symmetry.
The parallelepiped has its "origin" at (xlo,ylo,zlo) and is defined by
3 edge vectors starting from the origin given by <B>a</B> = (xhi-xlo,0,0); <B>b</B>
= (xy,yhi-ylo,0); <B>c</B> = (xz,yz,zhi-zlo). <I>Xy,xz,yz</I> can be 0.0 or
positive or negative values and are called "tilt factors" because they
are the amount of displacement applied to faces of an originally
orthogonal box to transform it into the parallelepiped. Note that in
LAMMPS the triclinic simulation box edge vectors <B>a</B>, <B>b</B>, and <B>c</B> cannot be
arbitrary vectors. As indicated, <B>a</B> must be aligned with the x axis, <B>b</B>
must be in the xy plane, and <B>c</B> is arbitrary. However, this is not a
restriction since it is possible to rotate any set of 3 crystal basis
vectors so that they meet this restriction.
<P>LAMMPS also allows simulations to be perfored in triclinic
(non-orthogonal) simulation boxes shaped as a parallelepiped with
triclinic symmetry. The parallelepiped has its "origin" at
(xlo,ylo,zlo) and is defined by 3 edge vectors starting from the
origin given by <B>a</B> = (xhi-xlo,0,0); <B>b</B> = (xy,yhi-ylo,0); <B>c</B> =
(xz,yz,zhi-zlo). <I>Xy,xz,yz</I> can be 0.0 or positive or negative values
and are called "tilt factors" because they are the amount of
displacement applied to faces of an originally orthogonal box to
transform it into the parallelepiped. Note that in LAMMPS the
triclinic simulation box edge vectors <B>a</B>, <B>b</B>, and <B>c</B> cannot be
arbitrary vectors. As indicated, <B>a</B> must be aligned with the x axis,
<B>b</B> must be in the xy plane, and <B>c</B> is arbitrary. However, this is
not a restriction since it is possible to rotate any set of 3 crystal
basis vectors so that they meet this restriction.
</P>
<P>There is no requirement that a triclinic box be periodic in any
dimension, though it typically should be in at least the 2nd dimension
of the tilt (y in xy) if you want to enforce a shift in periodic
boundary conditions across that boundary. Some commands that work
with triclinic boxes, e.g. the <A HREF = "fix_deform.html">fix deform</A> and <A HREF = "fix_nh.html">fix
npt</A> commands, require periodicity or non-shrink-wrap
boundary conditions in specific dimensions. See the command doc pages
for details.
</P>
<P>The 9 parameters (xlo,xhi,ylo,yhi,zlo,zhi,xy,xz,yz) are defined at the
time the simluation box is created. This happens in one of 3 ways.