Added fcc and bcc examples for the Steinhardt-Nelson parameters

doc/src/compute_orientorder_atom.txt

@@ -27,7 +27,7 @@ keyword = {cutoff} or {nnn} or {degrees} or {components}
 
 compute 1 all orientorder/atom
 compute 1 all orientorder/atom degrees 5 4 6 8 10 12 nnn NULL cutoff 1.5
-compute 1 all orientorder/atom degrees 4 6 components 6 nnn NULL cutoff 3.0 :pre
+compute 1 all orientorder/atom degrees 2 4 6 components 6 nnn NULL cutoff 3.0 :pre
 
 [Description:]
 
@@ -48,7 +48,7 @@ neighbors of the central atom.
 The angles theta and phi are the standard spherical polar angles
 defining the direction of the bond vector {rij}.
 The second equation defines {Ql}, which is a
-rotationally invariant scalar quantity obtained by summing
+rotationally invariant non-negative amplitude obtained by summing
 over all the components of degree {l}.
 
 The optional keyword {cutoff} defines the distance cutoff

src/steinhardt/in.bcc

@@ -0,0 +1,47 @@
+# 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}
+
+# initial velocities
+
+velocity     all create 5.0 482748
+fix	     1 all nve
+
+# 8 neighbors, perfect crystal
+
+compute 	qn all orientorder/atom degrees 5 4 6 8 10 12 nnn 8
+compute 	avqn all reduce ave c_qn[*] 
+
+thermo_style    custom step temp epair etotal c_avqn[*]
+
+run		0
+
+# 14 neighbors, perfect crystal dynamically melting
+
+uncompute       qn
+compute 	qn all orientorder/atom degrees 5 4 6 8 10 12 nnn 14
+
+timestep	0.003
+thermo		1
+
+run		20

src/steinhardt/in.fcc

@@ -0,0 +1,39 @@
+# Steinhardt-Nelson bond orientational order parameters for FCC
+
+variable  	rcut equal 3.0
+
+boundary	p p p
+
+atom_style	atomic
+neighbor	0.3 bin
+neigh_modify	delay 5
+
+# create geometry
+
+lattice		fcc 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}
+
+# initial velocities
+
+velocity     all create 5.0 482748
+fix	     1 all nve
+
+# 12 neighbors, perfect crystal dynamically melting
+
+compute 	qn all orientorder/atom # degrees 5 4 6 8 10 12 nnn 12
+compute 	avqn all reduce ave c_qn[*] 
+
+timestep	0.003
+thermo_style    custom step temp epair etotal c_avqn[*]
+thermo		1
+
+run		20