how to correctly simulate the screw dislocation core in bcc

hi everyone,

I’m simulating the bcc screw dislocation core structure using the lammps.

The material is bcc-Fe, ab-initio predicts it has a compact core. Also it was told in papers that the Mendelev type potentials can reproduce that kind of core structure.(potential 2 in Phil. Mag., 83 3977-3994 (2003))

However, with my scripts, I always get a split core, though it can reproduce the core structure by Ackland 97 potential.

Could you kindly tell me where to find some detailed tutorial on this? where I made it wrong?

I attached my scripts. Using do MS simulation, then postprocessed by core.f90, then using asymptote script s.asy to draw the differential displacement map.

I want to use the lammps to built the dislocation dipole, so somehow the dipole building looks strange in my script, though it should work. And in the asy script, the final task of scale arrow length with 1/3b is not performed.

There is also a related problem: the easy core and hard core 1/2<111> dislocation core, do they have energy difference? Is this depending on potentials?

Thanks in advance! (3.58 KB)

core.f90 (2.73 KB)

s.asy (673 Bytes)