[lammps-users] How to set option of NVT for non-periodic system!

Dear Lammps_users

    I take NVT fix to equilibrate a nanowire with both end fixed.
      But NVT fix doesn't work well.
      I changed the parameters of NVT in many ways.
      While, it always collapsed.
      I also read the closer question which was asked on the mail-list
      and run with the recommended parameters. It does not work too.

      Is there some additional option for the non-periodic system?
      Or some errors in my input?
      Any suggestion will be apprecated!
-------------Input file----------------
variable x index 30
variable y index 2.5
variable z index 2.5
variable v equal 0.1
variable c equal 2
variable d equal 28

units metal
atom_style atomic

neighbor 2.0 bin
neigh_modify every 1 delay 5 check yes

# Creat geometry

dimension 3
boundary s s s

lattice fcc 3.52

region box block 0 $x 0 $y 0 $z
create_box 1 box
create_atoms 1 box

# Creat group
region left block 0 $c 0 $y 0 $z
group fixed region left
region midd block $c $d 0 $y 0 $z
group belt region midd
region right block $d $x 0 $y 0 $z
group pull region right
group boundary union fixed pull

# EAM potentials

pair_style eam
pair_coeff 1 1 niu3

# Initial velocites

temperature wendu all full
velocity all create 300.0 887723 temp wendu

# Fixes

fix 1 belt nvt 300.0 300.0 0.1 drag 0.2
fix 2 boundary setforce 0.0 0.0 0.0

# Equilibrate (20 ps)

minimize 1.0e-4 100 1000

dump 1 all atom 50 eq_100_10.xyz
dump_modify 1 header xyz

thermo 50
thermo_modify temp wendu

timestep 0.001
run 20000

Best Regards

Zhenyu Yang
  State Key Laboratory of Nonlinear Mechanics (LNM)
  Institute of Mechanics, Chinese Academy of Sciences
  No.15 Beisihuanxi Road
  Beijing 100080, P. R. China
  FAX: 010-62579511
[email protected]...