# change_box delta command

Hi all,

I am using lammps version March 31, 2017. I am trying to simulate an anisotropic system with non-periodic boundary condition along z direction of a box. I wanted to change the box boundary along z after some intervals. Initially, the box boundaries were

orthogonal box = (5.961 5.961 5.96087) to (21.1832 21.1832 23.4232)

I used change_box command as shown:

change_box all z delta 0.0 2.24 boundary p p m units box
orthogonal box = (5.66715 5.66715 5.42676) to (21.477 21.477 26.6443)

As I mentioned the change in lower boundary of z is 0 then why it gets changed?. As I used it for multiple times and lower z value is changing inspite of change in zlo is 0. Also, the change is not 2.24, it is greater than 2.24. What is the reason behind this?

Hi all,

I am using lammps version March 31, 2017. I am trying to simulate an
anisotropic system with non-periodic boundary condition along z direction
of a box. I wanted to change the box boundary along z after some intervals.
Initially, the box boundaries were

orthogonal box = (5.961 5.961 5.96087) to (21.1832 21.1832 23.4232)

I used change_box command as shown:

change_box all z delta 0.0 2.24 boundary p p m units box
orthogonal box = (5.66715 5.66715 5.42676) to (21.477 21.477 26.6443)

As I mentioned the change in lower boundary of z is 0 then why it gets
changed?. As I used it for multiple times and lower z value is changing
inspite of change in zlo is 0. Also, the change is not 2.24, it is greater
than 2.24. What is the reason behind this?

​there is not enough information here to make an assessment of wh​at is
going on with sufficient confidence.
most likely there are operations happening between the original creation of
the simulation box and the point where you issue the change_box command.
when i run the following input:

region box block 6 20 6 20 6 20
create_box 1 box
change_box all z delta 0.0 2.24 boundary p p m units box

i get the expected behavior:

\$ ./lmp_omp -in in.box
LAMMPS (1 Sep 2017)