lammps/examples/steinhardt/in.bcc

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# Steinhardt-Nelson bond orientational order parameters for BCC
variable rcut equal 3.0
boundary p p p
atom_style atomic
neighbor 0.3 bin
neigh_modify delay 5
# create geometry
lattice bcc 1.0
region box block 0 3 0 3 0 3
create_box 1 box
create_atoms 1 box
mass 1 1.0
# LJ potentials
pair_style lj/cut ${rcut}
pair_coeff * * 1.0 1.0 ${rcut}
# 14 neighbors, perfect crystal
compute qlwlhat all orientorder/atom degrees 6 2 4 6 8 10 12 nnn 14 wl/hat yes
compute avql all reduce ave c_qlwlhat[1] c_qlwlhat[2] c_qlwlhat[3] c_qlwlhat[4] c_qlwlhat[5] c_qlwlhat[6]
compute avwlhat all reduce ave c_qlwlhat[7] c_qlwlhat[8] c_qlwlhat[9] c_qlwlhat[10] c_qlwlhat[11] c_qlwlhat[12]
thermo_style custom step temp epair etotal c_avql[*] c_avwlhat[*]
run 0
# check Q_l values
print " "
print "*******************************************************************"
print " "
print "Comparison with reference values of Q_l "
print " [Table I in W. Mickel, S. C. Kapfer,"
print " G. E. Schroeder-Turkand, K. Mecke, "
print " J. Chem. Phys. 138, 044501 (2013).]"
print " "
variable q2ref equal 0.0
variable q4ref equal 0.036
variable q6ref equal 0.511
variable q8ref equal 0.429
variable q10ref equal 0.195
variable q12ref equal 0.405
variable q2 equal c_avql[1]
variable q4 equal c_avql[2]
variable q6 equal c_avql[3]
variable q8 equal c_avql[4]
variable q10 equal c_avql[5]
variable q12 equal c_avql[6]
print "q2 = $(v_q2:%10.6f) delta = $(v_q2-v_q2ref:%10.4f)"
print "q4 = $(v_q4:%10.6f) delta = $(v_q4-v_q4ref:%10.4f)"
print "q6 = $(v_q6:%10.6f) delta = $(v_q6-v_q6ref:%10.4f)"
print "q8 = $(v_q8:%10.6f) delta = $(v_q8-v_q8ref:%10.4f)"
print "q10 = $(v_q10:%10.6f) delta = $(v_q10-v_q10ref:%10.4f)"
print "q12 = $(v_q12:%10.6f) delta = $(v_q12-v_q12ref:%10.4f)"
# check W_l_hat values
print " "
print "Comparison with reference values of W_l_hat"
print " [Table I in P. Steinhardt, D. Nelson, and M. Ronchetti, "
print " Phys. Rev. B 28, 784 (1983).]"
print " "
variable w4hatref equal 0.159317
variable w6hatref equal 0.013161
variable w8hatref equal -0.058455
variable w10hatref equal -0.090130
variable w4hat equal c_avwlhat[2]
variable w6hat equal c_avwlhat[3]
variable w8hat equal c_avwlhat[4]
variable w10hat equal c_avwlhat[5]
print "w4hat = $(v_w4hat:%10.6f) delta = $(v_w4hat-v_w4hatref:%10.6f)"
print "w6hat = $(v_w6hat:%10.6f) delta = $(v_w6hat-v_w6hatref:%10.6f)"
print "w8hat = $(v_w8hat:%10.6f) delta = $(v_w8hat-v_w8hatref:%10.6f)"
print "w10hat = $(v_w10hat:%10.6f) delta = $(v_w10hat-v_w10hatref:%10.6f)"
print " "
print "*******************************************************************"
print " "