EOS: make

Step 1. Before make in EOS, the equilibrium configuration CONTCAR must be present in confs/mp-*/relaxation.

Step 2. For the input example in the previous section, when we do make, 40 tasks would be generated as confs/mp-*/eos_00/task.000000, confs/mp-*/eos_00/task.000001, ... , confs/mp-*/eos_00/task.000039. The suffix 00 is used for possible refine later.

Step 3. If the task directory, for example confs/mp-*/eos_00/task.000000 is not empty, the old input files in it including INCAR, POSCAR, POTCAR, conf.lmp, in.lammps would be deleted.

Step 4. In each task directory, POSCAR.orig would link to confs/mp-*/relaxation/CONTCAR. Then the scale parameter can be calculated as:

scale = (vol_current / vol_equi) ** (1. / 3.)

vol_current is the corresponding volume per atom of the current task and vol_equi is the volume per atom of the equilibrium configuration. Then the poscar_scale function in dpgen.auto_test.lib.vasp module would help to generate POSCAR file with vol_current in confs/mp-*/eos_00/task.[0-9]*[0-9].

Step 5. According to the task type, the input file including INCAR, POTCAR or conf.lmp, in.lammps would be written in every confs/mp-*/eos_00/task.[0-9]*[0-9].

For EOS calculations by VASP, if change_box is True, ISIF in VASP would be 4, else ISIF would be 2. The default value of change_box is True. For further information of the use of ISIF in VASP, we refer users to ISIF command.

For EOS calculations by LAMMPS, when change_box is True, an example of in.lammps for AlMg is given as below and the scale parameter in line 5 is calculated by the equation above.

clear
variable        GPa2bar	equal 1e4
variable        B0	equal 70
variable        bp	equal 0
variable	xx	equal scale
variable        yeta	equal 1.5*(${bp}-1)
variable        Px0	equal 3*${B0}*(1-${xx})/${xx}^2*exp(${yeta}*(1-${xx}))
variable        Px	equal ${Px0}*${GPa2bar}
units           metal
dimension       3
boundary	p p p
atom_style	atomic
box             tilt large
read_data       conf.lmp
mass            1 1
mass            2 1
neigh_modify    every 1 delay 0 check no
pair_style      deepmd frozen_model.pb
pair_coeff
compute         mype all pe
thermo          100
thermo_style    custom step pe pxx pyy pzz pxy pxz pyz lx ly lz vol c_mype
dump            1 all custom 100 dump.relax id type xs ys zs fx fy fz
min_style       cg
fix             1 all box/relax iso ${Px}
minimize        1.000000e-12 1.000000e-06 5000 500000
fix             1 all box/relax aniso ${Px}
minimize        1.000000e-12 1.000000e-06 5000 500000
variable        N equal count(all)
variable        V equal vol
variable        E equal "c_mype"
variable        Pxx equal pxx
variable        Pyy equal pyy
variable        Pzz equal pzz
variable        Pxy equal pxy
variable        Pxz equal pxz
variable        Pyz equal pyz
variable        Epa equal ${E}/${N}
variable        Vpa equal ${V}/${N}
print "All done"
print "Total number of atoms  = ${N}"
print "Relax at Press         = ${Px} Bar"
print "Final energy per atoms = ${Epa} eV"
print "Final volume per atoms = ${Vpa} A^3"
print "Final Stress (xx yy zz xy xz yz) = ${Pxx} ${Pyy} ${Pzz} ${Pxy} ${Pxz} ${Pyz}"

when change_box is False, an example of in.lammps for AlMg is given as:

clear
units 	metal
dimension	3
boundary	p	p    p
atom_style	atomic
box         tilt large
read_data   conf.lmp
mass            1 1
mass            2 1
neigh_modify    every 1 delay 0 check no
pair_style deepmd frozen_model.pb
pair_coeff
compute         mype all pe
thermo          100
thermo_style    custom step pe pxx pyy pzz pxy pxz pyz lx ly lz vol c_mype
dump            1 all custom 100 dump.relax id type xs ys zs fx fy fz
min_style       cg
minimize        1.000000e-12 1.000000e-06 5000 500000
variable        N equal count(all)
variable        V equal vol
variable        E equal "c_mype"
variable        tmplx equal lx
variable        tmply equal ly
variable        Pxx equal pxx
variable        Pyy equal pyy
variable        Pzz equal pzz
variable        Pxy equal pxy
variable        Pxz equal pxz
variable        Pyz equal pyz
variable        Epa equal ${E}/${N}
variable        Vpa equal ${V}/${N}
variable        AA equal (${tmplx}*${tmply})
print "All done"
print "Total number of atoms = ${N}"
print "Final energy per atoms = ${Epa}"
print "Final volume per atoms = ${Vpa}"
print "Final Base area = ${AA}"
print "Final Stress (xx yy zz xy xz yz) = ${Pxx} ${Pyy} ${Pzz} ${Pxy} ${Pxz} ${Pyz}"