removed a bug in fix_neb.cpp which prevented the freeend to work properly,...

removed a bug in fix_neb.cpp which prevented the freeend to work properly, plus added an example for the neb freeend

examples/neb/in.neb.hop1freeend

+# 2d NEB surface simulation, hop from surface to become adatom
+
+dimension	2
+boundary	p s p
+
+atom_style	atomic
+neighbor	0.3 bin
+neigh_modify	delay 5
+atom_modify	map array sort 0 0.0
+
+variable	u uloop 20
+
+# create geometry with flat surface
+
+lattice		hex 0.9
+region		box block 0 20 0 10 -0.25 0.25
+
+read_data        initial.hop1freeend
+
+# LJ potentials
+
+pair_style	lj/cut 2.5
+pair_coeff	* * 1.0 1.0 2.5
+pair_modify	shift yes
+
+# define groups
+
+region	        1 block INF INF INF 1.25 INF INF
+group		lower region 1
+group		mobile subtract all lower
+set		group lower type 2
+
+timestep	0.05
+
+# group of NEB atoms - either block or single atom ID 412
+
+region		surround block 10 18 17 20 0 0 units box
+group		nebatoms region surround
+#group		nebatoms id 412
+set		group nebatoms type 3
+group		nonneb subtract all nebatoms
+
+fix		1 lower setforce 0.0 0.0 0.0
+fix		2 nebatoms neb 1.0 freeend ini
+fix		3 all enforce2d
+
+thermo		100
+
+#dump		1 nebatoms atom 10 dump.neb.$u
+#dump		2 nonneb atom 10 dump.nonneb.$u
+
+# run NEB for 2000 steps or to force tolerance
+
+min_style	quickmin
+
+neb		0.0 0.1 1000 1000 100 final final.hop1