# calculate the energy volume curve for InP zincblende

# define volume range and filename

variable	ndelta equal 100
variable	volatom_min equal 20.0
variable	volatom_max equal 29.0
variable	evsvolfile string evsvol.dat

# set up cell 

units		metal
 
boundary	p p p

# setup loop variables for box volume

variable	amin equal ${volatom_min}^(1/3)*2
variable 	delta equal (${volatom_max}-${volatom_min})/${ndelta} 
variable	scale equal (${delta}/v_volatom+1)^(1/3)

# set up 8 atom InP zincblende unit cell

lattice diamond ${amin}

region		box prism &
	 	0 1 &
		0 1 &
		0 1 &
		0 0 0

create_box	2 box

create_atoms	1	box       &
			basis 5 2 &
			basis 6 2 &
			basis 7 2 &
			basis 8 2

mass 		1 114.76
mass 		2 30.98

# choose potential

pair_style	vashishta
pair_coeff 	* * InP.vashishta In P

# setup neighbor style

neighbor 	1.0 nsq
neigh_modify 	once no every 1 delay 0 check yes

# setup output

thermo_style 	custom step temp pe press vol
thermo_modify 	norm no
variable 	volatom equal vol/atoms
variable 	eatom equal pe/atoms
print 		"# Volume [A^3/atom] Energy [eV/atom]" file ${evsvolfile}

# loop over range of volumes

label 		loop
variable 	i loop ${ndelta}

change_box 	all x scale ${scale} y scale ${scale} z scale ${scale} remap

# calculate energy
# no energy minimization needed for zincblende
 
run 		0
print 		"${volatom} ${eatom}" append ${evsvolfile}

next 		i
jump 		SELF loop