- It is not clear to me how to use the fix box/relax command to minimize energy while allowing the box size to change. When I use the lines given below, nothing happens. That is, everything in the thermodynamic output remains same.
….
….
lattice fcc 4.05 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1
……
velocity all create 300.0 5812775
fix 2 all box/relax aniso 0.0 0.0 4000.0
minimize 1.0e-7 0.001 10000 100000
unfix 2
minimize 1.0e-7 0.001 10000 100000
#2
fix 2 all box/relax aniso 0.0 0.0 2000.0
minimize 1.0e-7 0.001 10000 100000
unfix 2
minimize 1.0e-7 0.001 10000 100000
But when I change the orientation by the command:
lattice fcc 4.05 orient x 1 1 1 orient y 1 1 -2 orient z -1 1 0
(i.e. z = face diagonal or close packed direction), energy decreases with time step and the pressure in z direction approaches the value in fix box/relax. However, with the minimize command after the ‘unfix 2’, minimization goes on for a few more time steps (without change in box dimensions) changing both the pressure and the energy. It seems then, that the minimization done with ‘fix box/relax’ did not really give a configuration with the lowest energy for the final volume.
Why is this so?
Why should orientation of the lattice affect the minimization?
Furthermore, when I did not use a standalone minimization command (i.e. after unfix 2 box/relax) and with the orientation #2, minimization stopped after a few repetitions of the above sequence with different z pressures. That is, the minimization did not try to attain the specified pressure.
- I am also getting the message “Resetting reneighboring criterion during minimization’.
Is it something that I should be concerned about?
Thanks
Rohit