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[lammps-users] Setting a time-dependent dipole moment
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[lammps-users] Setting a time-dependent dipole moment


From: Antonio Ortiz <aortiza@...7014...>
Date: Mon, 24 Jul 2017 17:16:00 +0000

Hello,

I'm trying to set a time dependent dipole moment for a pair of particles by calculating a variable with:
and then I write:
The problem is that instead of assigning the value of the calculated variable to the z component of the dipole moment, it assigns zero. Even if I set the initial value to something other than zero, the set command will put it back to zero. 

However if I dump the value of v_Field, it is being updated every loop. Also, if I substitute time for xlo, the calculated value is correctly set to the dipole moment. The same problem arises if I try to set the position to a time dependent variable. 

I'm sending a working example.

Thanks in advance,
Antonio Ortiz. 

----- LAMMPS Input File -----
units micro
atom_style hybrid sphere dipole bond
boundary s s p
dimension 3
neighbor 4.0 nsq
pair_style lj/cut/dipole/cut 20

read_data TimeDependentInput.data

group Atoms type 1
mass * 1

timestep 10000

variable thermoname equal time/1e9
variable Field atom time*1e-9

set group Atoms dipole 0 0 v_Field

dump 3 all custom 10 TimeDependentField.lammpstrj id type x y z v_Field muz
thermo_style custom step atoms v_thermoname
thermo 1000

run 6000

----- TimeDependentInput.data File -----
4 atoms
2 atom types
-30.00 30.00 xlo xhi 
-30.00 30.00 ylo yhi 
-1.50 1.50 zlo zhi 

Atoms

     1 2 15.00 0.00 0.000000 10.30 0.0017 0.0     0    0     0 1
     2 2 -15.00 0.00 0.000000 10.30 0.0017 0.0     0    0     0 2
     3 1 15.01 0.00 0.014681 10.30 0.001678 0.0 0.0 0.0     0.002 1
     4 1 -15.01 0.00 0.016334 10.30 0.001678 0.0 0.0 0.0     0.002 2

PairIJ Coeffs

1 1 0.0 0.0 0.0 60.000000
1 2 0.0 0.0 0.0 0.0 
2 2 0.0 0.0 0.0 0.0