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lammps/examples/elastic/displace.mod
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displace.mod
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# NOTE: This script should not need to be
# modified. See in.elastic for more info.
#
# Find which reference length to use
if ${dir} == 1 then &
"variable len0 equal ${lx0}"
if ${dir} == 2 then &
"variable len0 equal ${ly0}"
if ${dir} == 3 then &
"variable len0 equal ${lz0}"
if ${dir} == 4 then &
"variable len0 equal ${lz0}"
if ${dir} == 5 then &
"variable len0 equal ${lz0}"
if ${dir} == 6 then &
"variable len0 equal ${ly0}"
# Reset box and simulation parameters
clear
read_restart restart.equil
include potential.mod
# Negative deformation
variable delta equal -${up}*${len0}
if ${dir} == 1 then &
"displace_box all x delta 0 ${delta} units box"
if ${dir} == 2 then &
"displace_box all y delta 0 ${delta} units box"
if ${dir} == 3 then &
"displace_box all z delta 0 ${delta} units box"
if ${dir} == 4 then &
"displace_box all yz delta ${delta} units box"
if ${dir} == 5 then &
"displace_box all xz delta ${delta} units box"
if ${dir} == 6 then &
"displace_box all xy delta ${delta} units box"
# Relax atoms positions
minimize ${etol} ${ftol} ${maxiter} ${maxeval}
# Obtain new stress tensor
variable tmp equal pxx
variable pxx1 equal ${tmp}
variable tmp equal pyy
variable pyy1 equal ${tmp}
variable tmp equal pzz
variable pzz1 equal ${tmp}
variable tmp equal pxy
variable pxy1 equal ${tmp}
variable tmp equal pxz
variable pxz1 equal ${tmp}
variable tmp equal pyz
variable pyz1 equal ${tmp}
# Compute elastic constant from pressure tensor
variable C1neg equal ${d1}
variable C2neg equal ${d2}
variable C3neg equal ${d3}
variable C4neg equal ${d4}
variable C5neg equal ${d5}
variable C6neg equal ${d6}
# Reset box and simulation parameters
clear
read_restart restart.equil
include potential.mod
# Positive deformation
variable delta equal ${up}*${len0}
if ${dir} == 1 then &
"displace_box all x delta 0 ${delta} units box"
if ${dir} == 2 then &
"displace_box all y delta 0 ${delta} units box"
if ${dir} == 3 then &
"displace_box all z delta 0 ${delta} units box"
if ${dir} == 4 then &
"displace_box all yz delta ${delta} units box"
if ${dir} == 5 then &
"displace_box all xz delta ${delta} units box"
if ${dir} == 6 then &
"displace_box all xy delta ${delta} units box"
# Relax atoms positions
minimize ${etol} ${ftol} ${maxiter} ${maxeval}
# Obtain new stress tensor
variable tmp equal pe
variable e1 equal ${tmp}
variable tmp equal press
variable p1 equal ${tmp}
variable tmp equal pxx
variable pxx1 equal ${tmp}
variable tmp equal pyy
variable pyy1 equal ${tmp}
variable tmp equal pzz
variable pzz1 equal ${tmp}
variable tmp equal pxy
variable pxy1 equal ${tmp}
variable tmp equal pxz
variable pxz1 equal ${tmp}
variable tmp equal pyz
variable pyz1 equal ${tmp}
# Compute elastic constant from pressure tensor
variable C1pos equal ${d1}
variable C2pos equal ${d2}
variable C3pos equal ${d3}
variable C4pos equal ${d4}
variable C5pos equal ${d5}
variable C6pos equal ${d6}
# Combine positive and negative
variable C1${dir} equal 0.5*(${C1neg}+${C1pos})
variable C2${dir} equal 0.5*(${C2neg}+${C2pos})
variable C3${dir} equal 0.5*(${C3neg}+${C3pos})
variable C4${dir} equal 0.5*(${C4neg}+${C4pos})
variable C5${dir} equal 0.5*(${C5neg}+${C5pos})
variable C6${dir} equal 0.5*(${C6neg}+${C6pos})
# Delete dir to make sure it is not reused
variable dir delete
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