energy minimization

Hi lammps users,

I came across a very simple problem when doing energy minimization, this is my input script:

variable etol equal 0.0

variable ftol equal 1.0e-10

variable maxiter equal 10000

variable maxeval equal 10000

variable dmax equal 1.0e-2

boundary p p p

units metal

atom_style atomic

#lattice fcc 3.61 orient x -1 0 1 orient y 1 -2 1 orient z 1 1 1

lattice fcc 3.61 orient x 1 0 0 orient y 0 1 0 orient z 0 0 1

region myreg block 0 2 0 2 -2 2

create_box 1 myreg

create_atoms 1 box

pair_style eam

pair_coeff * * Cu_u3.eam

neighbor 3.0 bin

min_style cg

dump 1 all custom 10 dump.minimize id type x y z

minimize {etol} {ftol} {maxiter} {maxeval}

when the axis orientation is “x 1 0 0 y 0 1 0 z 0 0 1”, there are no differentce between the initial atomic structure and the one after energy minimization. But when the axis orientation is “x -1 0 1 y 1 -2 1 z 1 1 1”the initial atomic structure will change after energy minimization, and I feel this is rather weird. I have tried other axis orientation “x 1 1 1 y 1 -1 0 z 1 1 -2” and other potential, or change the material from Cu to Ni, but the results are same: the initial structure except for “x -1 0 1 y 0 1 0 z 0 0 1” will change.

Any help will be appreciated.

All the best.

Lily

Hi lammps users,

I came across a very simple problem when doing energy minimization, this is
my input script:

[...]

when the axis orientation is “x 1 0 0 y 0 1 0 z 0 0 1”, there are no
differentce between the initial atomic structure and the one after energy
minimization. But when the axis orientation is “x -1 0 1 y 1 -2 1 z 1 1
1”the initial atomic structure will change after energy minimization, and I
feel this is rather weird. I have tried other axis orientation “x 1 1 1 y 1

i don't feel that this is weird at all. this is basic crystal
structure knowledge.
you have chosen an orientation, where you need to have a simulation
cell length in y-direction that needs to be a multiple of 3 of the
lattice spacing in order to have a perfect continuation across
periodic boundaries.

change your box to:

region myreg block 0 2 0 3 -2 2

and you will see.

axel.