# [lammps-users] APB energy at finite temperature

Hello,

I want to calculate the anti-phase boundary (APB) energy at finite temperatures. I found the following steps in literature to obtain APB energy at 0 K:

1- generate the lattice such that one orientation is along the slip plane normal direction.
2- displace half the system in the specific direction
3- restrict the lateral movement of the displaced section in the slip plane. and determine periodic BC in lateral to slip plane and free boundary in

4- minimize the energy

But, has anyone have any experience in calculating APB energy at finite temperatures? I have tried different ensembles in step 4 such as "NPT with using barostat only in the direction parallel to normal to slip plane " and “temp/rescale”, but did not obtain reasonable results.

Does any one have any idea on the last step’s energy minimization at finite temperature?

Best,
Sepideh

[…]

Does any one have any idea on the last step’s energy minimization at finite temperature?

there is no such thing like energy minimization at finite temperature.

statistical mechanics tells us that at finite temperature you don’t have a single minimal state, but rather a collection of states of the same total energy with different individual positions/velocities and thus different decomposition of the total energy into potential and kinetic energy. if coupled to a heat bath through a thermostat, then you have to consider that one as well; same for a barostat.

axel.