Hi all,
I recently ran two equivalent simulations of a Sigma 5 36.7 degree twist grain boundary, one with the Al99.eam.alloy potential by Mishin et al (1999) and another with the most recent, Al_wkg potential by Winey et al (2009).
I will admit that minimising the grain boundary energy is not a “thermoelastic effect”, however I am surprised by the striking contrast in energies produced. Here is a comparison of the outputs:
######Al_wkg
GB energy is 21204.014846177542495
Comparative GB energy is 25031.43417515134206
######Al99.eam.alloy
GB energy is 243.14689466352155023
Comparative GB energy is 269.84369126549887596
######### Input script:
units metal
dimension 3
boundary p p p
atom_style atomic
lattice fcc 4.05 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
region whole block 0 15 -10 10 0 15
create_box 1 whole
lattice fcc 4.05 orient x 8 0 6 orient y 0 10 0 orient z -6 0 8
region top block 0 15 0 10 0 15
create_atoms 1 region top
lattice fcc 4.05 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
region bottom block 0 15 -10 0 0 15
delete_atoms region bottom
create_atoms 1 region bottom
pair_style eam/alloy
pair_coeff * * Al99.eam.alloy Al
group topg region top
group bottomg region bottom
Define region away from PBCs (least likely influenced)
region centre block 5 10 -5 5 5 10
group centre region centre
delete_atoms overlap 1.0 bottomg topg
compute csym all centro/atom fcc
compute pe all pe/atom
compute pen all pe
compute PEsum all reduce sum c_pe
############### Compute the energy of the group of interest, near the centre of the GB
compute PEcentre centre reduce sum c_pe
thermo 50
thermo_style custom step lx ly lz etotal pe temp
shell mkdir template_GB
shell cd template_GB
dump 1 all cfg 25 dump_GBIndent_*.cfg id type xs ys zs c_csym c_pe fx fy fz
dump_modify 1 element Al
min_style cg
minimize 1.0e-15 1.0e-15 99999 999999
fix 1 all box/relax y 0.0 vmax 0.0001
minimize 1.0e-15 1.0e-15 10000 20000
thermo 1
reset_timestep 0
thermo_style custom step lx ly lz etotal pe temp c_PEsum c_PEcentre
run 10
variable gbArea equal “lxly2”
#variable gbArea2 equal “1288.252"
variable gbEtotal equal "etotal-(-3.3600count(all))”
variable GBE equal “v_gbEtotal/v_gbArea”
variable GBE_ equal “v_GBE*16021.7733”
#variable GBcompare equal “c_PEsum-(-3.3600count(all))"
#variable GBE2 equal “v_GBcompare/v_gbArea”
#variable GBE_2 equal "v_GBE216021.7733”
########################The GB area is assumed to be related to the total area in an equal ratio to the initialised value. Note, the “centre” group does not have half a GB on the top or bottom planes!! Thus, initial side lengths 5 and 5, compared to 15 and 15, the area should be 1/9 the original.
variable gbArea2 equal “lxly/9"
variable gbcentre equal "c_PEcentre-(-3.3600count(centre))”
variable GBE3 equal “v_gbcentre/v_gbArea2”
variable GBE_3 equal “v_GBE3*16021.7733”
print “GB energy is {GBE_}"
#print "Comparative GB energy is {GBE_2}”
print “Comparative GB energy is ${GBE_3}”
echo both