Is it possible to deform the simulation box in certain direction without changing the volume of the box?

Dear LAMMPS users,

I am trying to deform my simulation box as an analogy to the tensile test in the experiment. I found that fix deform can help me elongate the simulation box in, for example, z-direction, but the volume of the box will increase, while in the tensile test in the experiment the volume of the sample will nearly not change. So may I have your suggestion about how to deform the simulation box along certain direction without changing the volume, and the size of other dimensions changes “naturally” rather than I specify. Besides, in my simulation, I applied Brownian dynamics which means that I have both fix langevin and fix nve. Thank you in advance.

Best regards,
Wusheng

Dear LAMMPS users,

I am trying to deform my simulation box as an analogy to the tensile test
in the experiment. I found that fix deform can help me elongate the
simulation box in, for example, z-direction, but the volume of the box will
increase, while in the tensile test in the experiment the volume of the
sample will nearly not change. So may I have your suggestion about how to
deform the simulation box along certain direction without changing the
volume, and the size of other dimensions changes "naturally" rather than I
specify. Besides, in my simulation, I applied Brownian dynamics which means
that I have both fix langevin and fix nve. Thank you in advance.

​please note the "volume" option for fix deform. otherwise, you can use
deform on one dimension, and couple the other two to fix nph or npt or
press/berendsen with suitable choice of parameters. please also note, that
​when using a barostat option, you have to very carefully adjust the
deformation rate, so that the system remains close enough to equilibrium
and the barostat fixes have sufficient time to adjust the system volume.

axel.