Non-equilibrium MD (NEMD) for heat flux

One can perform NEMD heat flux simulation applying different temperatures at different regions. The figure below shows a setting of heat-flux NEMD simulation.

Heat flux must be flown along x-direction. In this case, at both left and right side of the system, atoms are fixed during simulation. And vacuum region is placed in order to avoid interactions between hot and cool atoms.

The digits at the bottom of above picture are ifmv values. The ifmv values of fixed atoms should be 0, hot atoms to be 2, cool atoms 3, intermediate atoms 1. And the temperature setting in in.pmd is like following,

initial_temperature     -600d0
temperature_control     Berendsen
temperature_target   1  -300d0
temperature_target   2  350d0
temperature_target   3  250d0
temperature_relax_time  100d0
factor_direction 3 3
  1.000d0  1.000d0  1.000d0
  1.000d0  1.000d0  1.000d0
  1.000d0  1.000d0  1.000d0

Target temperatures of hot and cool atoms are 350 K and 250 K. Whereas the target temperature of intermediate atoms are not set and the value is set negative.

Temperature distribution along x is obtained by specifying as follows in in.pmd,

flag_temp_dist  T
num_temp_dist  50

which means setting flag .true. and the number of bins along x is 50. The num_temp_dist value must be a multiple of num_nodes_x. Results will be written in out.temp-dist. The out.temp-dist file contains temperatures of 50 points of every num_iteration/ num_out_energy steps.