How to fix a group without moving

Hi all,
Following partial input script discribes a collision bewteen two unfixed groups. evrything is ok.
My question is how to fix the left group without moving , let right group move and compact on the left group.
I applied the “fix setforce” command to practice it. However, this command make a constraint of deformation for the left group.
i want the right group move and compact on a fixed left group, both of them can deform due to collision.
All your reply are appreciated.
##define two group

group left id <= ***
group right id >= ***

collision between two unfixed group.

fix 4 all nve

velocity left set v_l NULL NULL units box
velocity right set v_r NULL NULL units box

Yao

State Key Laboratory for Mechanical Behavior of Materials
School of Materials Science and Engineering, Xi’an Jiaotong University
Xianning West Road 28, Xi’an, Shaanxi, 710049 China
E-mail:[email protected]…127…

Hi all,
       Following partial input script discribes a collision bewteen two

incomplete inputs are useless. your mistake is likely elsewhere. what
is so difficult to understand about this???

i told you several times to not do this and be more concise and
complete in your problem description. if you don't care to respect the
wishes of people that volunteer their time to help you, the you are
not worth that time.

good luck (you're going to need it),
     axel.

Hi all,
   Following  input script discribes three groups of atoms. The down and left group were aparted from one block. Down group was fixed by the fix_setforce command and the left and right group were not. 

Then relaxed the system and computed the temperature of both left and right group. During second stage relaxation, the temperature of left group raised, and right group decreased. was this phenomenon normal or something was wrong in the input?

All your reply are appreciated.
units             real
dimension         3
newton            on
boundary          p p p
atom_style         hybrid  charge atomic
timestep       0.5
neighbor        2.0 nsq
neigh_modify    delay 0 every 1 check yes
read_data         data.TIO
  orthogonal box = (-100 -50 -50) to (200 50 50)
  1 by 1 by 1 MPI processor grid
  732 atoms
region 1 block INF -8 INF INF INF INF units box
region 2 block -8 6 INF INF INF INF units box
group            down    region 1
group            left    region 2
group            right id >= 367
#---------------Matsui-Akaogi potential-----------------------
pair_style buck/long/coul/long cut long 10.0
pair_coeff 1 1 7.177e+5 0.154 1.210e+2
pair_coeff 1 2 3.911e+5 0.194 2.904e+2
pair_coeff 2 2 2.717e+5 0.234 6.969e+2
pair_modify table 0
kspace_style  ewald 1.0e-4
Ewald initialization ...
  G vector (1/distance) = 0.233948
  estimated absolute RMS force accuracy = 0.0400463
  estimated relative force accuracy = 0.000120598
  KSpace vectors: actual max1d max3d = 41676 48 456336
Deleted 0 atoms, new total = 732
# ----------------computer energy
compute kineng_left  left ke
compute kineng_right  right ke
variable COM equal sqrt((v_position_L_x-v_position_R_x)*(v_position_L_x-v_position_R_x)+(v_position_L_y-v_position_R_y)*(v_position_L_y-v_position_R_y)+(v_position_L_z-v_position_R_z)*(v_position_L_z-v_position_R_z))
compute T_left left temp
compute T_right right temp/com
compute G left group/group right kspace yes
#------------------nitial velocity and temp
velocity all create 650.0 123456 dist gaussian units box
velocity down set 0.0 0.0 0.0 
###------------------fix---relax--nve+langevin-----------
<b>fix 1 all langevin 650.0 650.0 100.0 123456
fix 3 all nve</b>
thermo         10
thermo_style   custom step temp press pe ke etotal v_COM c_T_left c_T_right v_position_R_x v_position_L_x
thermo_modify  lost warn
run  5000
Ewald initialization ...
  G vector (1/distance) = 0.233948
  estimated absolute RMS force accuracy = 0.0400463
  estimated relative force accuracy = 0.000120598
  KSpace vectors: actual max1d max3d = 41676 48 456336
Memory usage per processor = 59.3772 Mbytes
Step Temp Press PotEng KinEng TotEng COM **T_left T_right** position position 
   0          650    17.366129   -213979.08    1416.3319   -212562.75     48.68356    655.06939    657.38961    47.343213   -1.3328319 
  1000    702.65427      2.89944   -214112.36    1531.0641   -212581.29    48.732232    702.62799    667.97969    47.350936   -1.372582
  2000    643.76548   -6.4069925   -214121.74     1402.747      -212719    48.796208     633.6014     650.3667    47.361723   -1.4225005 
  3000    703.40741    -2.669146   -214131.05    1532.7052   -212598.34    48.862564    712.57263    700.07463    47.378913   -1.4675413 
  4000    639.23676   -44.250022   -214220.79    1392.8791   -212827.91    48.814567    629.87041    644.54775    47.319238   -1.4718727 
  5000      645.521   -12.020412   -214219.39    1406.5723   -212812.82    48.721674    668.12761    632.92584    47.238412   -1.4587457 
Loop time of 5477.41 on 1 procs for 5000 steps with 732 atoms
Total # of neighbors = 87449
Ave neighs/atom = 119.466
Neighbor list builds = 17
Dangerous builds = 0
###-------------------fix---relax--nvt-----------
unfix 1
unfix 3
<b>fix 4 all nvt temp 650.0 650.0 10.0  drag 0.2 
fix 2 down setforce 0.0 0.0 0.0</b>
thermo         10
thermo_style   custom step temp press pe ke etotal v_COM c_T_left c_T_right v_position_R_x v_position_L_x
WARNING: New thermo_style command, previous thermo_modify settings will be lost (../output.cpp:663)
thermo_modify  lost warn
dump            1 all xyz 5000 dump.xyz.*
dump_modify     1 element Ti O
run             30000
Ewald initialization ...
  G vector (1/distance) = 0.233948
  estimated absolute RMS force accuracy = 0.0400463
  estimated relative force accuracy = 0.000120598
  KSpace vectors: actual max1d max3d = 41676 48 456336
Memory usage per processor = 59.5559 Mbytes
Step Temp Press PotEng KinEng TotEng COM **T_left T_right** position position 
    5000      645.521   -12.020412   -214219.39    1406.5723   -212812.82    48.721674    668.12761    632.92584    47.238412   -1.4587457 
    6000    670.85798    79.499234   -210314.26    1461.7808   -208852.48    48.480958    937.82575    452.57888    47.169016   -1.294666
    7000    652.21752   -13.283698   -211864.24    1421.1638   -210443.07    48.331888    1048.9292     323.7213    47.122235    -1.202682 
    8000    680.30414   -16.394656   -211618.03    1482.3638   -210135.67    48.368902    1114.1419    316.62062    47.084461   -1.280997 
   9310    639.65367   -17.787578   -211498.22    1393.7875   -210104.43    48.188966    1097.6215    245.15595    47.043526   -1.1348756
Interrupted ...............

Yao

State Key Laboratory for Mechanical Behavior of Materials
School of Materials Science and Engineering, Xi’an Jiaotong University
Xianning West Road 28, Xi’an, Shaanxi, 710049 China
E-mail:[email protected]…127…