git-svn-id: svn://svn.icms.temple.edu/lammps-ro/trunk@10777 f3b2605a-c512-4ea7-a41b-209d697bcdaa

examples/VISCOSITY/in.gk.2d

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+# sample LAMMPS input script for viscosity of 2d LJ liquid
+# Green-Kubo method via fix ave/correlate
+
+# settings
+
+variable	x equal 20
+variable	y equal 20
+
+variable	rho equal 0.6
+variable        t equal 1.0
+variable	rc equal 2.5
+
+variable    p equal 400     # correlation length
+variable    s equal 5       # sample interval
+variable    d equal $p*$s   # dump interval 
+
+# problem setup
+
+units		lj
+dimension	2
+atom_style	atomic
+neigh_modify	delay 0 every 1
+
+lattice         sq2 ${rho}
+region          simbox block 0 $x 0 $y -0.1 0.1
+create_box      1 simbox
+create_atoms    1 box
+
+pair_style      lj/cut ${rc}
+pair_coeff      * * 1 1
+
+mass            * 1.0
+velocity        all create $t 97287
+
+# equilibration run
+
+fix             1 all nve
+fix	        2 all langevin $t $t 0.1 498094
+fix	        3 all enforce2d
+
+thermo          $d
+run	        10000
+
+velocity	all scale $t
+
+unfix		2
+
+# Green-Kubo viscosity calculation
+
+reset_timestep  0
+
+variable         pxy equal pxy
+
+fix              SS all ave/correlate $s $p $d &
+                 v_pxy type auto file profile.gk.2d ave running
+
+variable         scale equal 1.0/$t*vol*$s*dt
+variable         v11 equal trap(f_SS[3])*${scale}
+
+thermo_style     custom step temp press pxy v_v11
+
+run              500000
+
+variable         eta equal v_v11
+print            "running average viscosity: ${eta}"