Birch-Murnaghan equation fitting for tetragonal structure

units metal
boundary p p p


pair_style tersoff
pair_coeff * * SiC.tersoff Si

variable lata equal 4.5
variable latc equal 2.4

fix my_print all print 1 "$(vol) $(pe)" file e.dat

variable my_count loop 50
label start
run 0
next my_count
jump SELF start

“how to fix code above with considering the anisotropy of tetragonal structure?”

Fix what?
This does effectively nothing.