LAMMPS WWW Site - LAMMPS Documentation - LAMMPS Mailing List Archives
[lammps-users] Dipole precessing in Electric Field
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[lammps-users] Dipole precessing in Electric Field

From: carles calero <carles.calero@...24...>
Date: Thu, 12 Oct 2017 06:34:22 -0400


I have performed a simple test to check the behavior of point dipoles in electric fields and the outcome seems to indicate that there is something wrong.

Basically, I run a simulation with one point dipole initially directed along the Z-direction in a static field directed along the Y-direction. The particle starts with zero velocity and I run the simulation in the nve ensemble (see below). I would expect a precession about the Y-axis, but instead I get a partial precession about the X-axis. By "partial precession" I mean that the moment rotates 180 degrees and then goes backwards. Both, the direction of precession and the trajectory seem to be unphysical.

I didn't find any reference to this problem in the mailing list.

I define the atom using:
atom_style    hybrid sphere dipole bond

The field is given by:
fix 0 dip1 efield 0.0 10.0 0.0

I use the integrator:
fix 2 all nve/sphere update dipole

The whole script is:
units        lj
atom_style    hybrid sphere dipole bond
bond_style      harmonic
dimension    3

read_data    input

pair_style    lj/cut/dipole/cut 10.0

pair_coeff 1 1 1.0 1.0 5.0 10.0
bond_coeff 1 1.0 4.0

group        dip1 type 1

velocity     all zero linear

fix 0 dip1 efield 0.0 10.0 0.0
fix 2 all nve/sphere update dipole

timestep    0.05
compute         t1 all temp/sphere
thermo_modify   temp t1

thermo        500

dump        0 dip1 custom 100 dump.dipole id type x y z mux muy muz
dump        1 all atom 1000 dump.lammpstrj

timestep     0.0001
thermo        50
run        1000000