[gmx-users] Uniaxial elongation using deform option

[Pragati Sharma]

Dear all,

I want to calculate young's modulus of a polymer using uniaxial elongation.
(elongation in z axis but no volume change)
I am using 'deform' option and semiisotropic pressure coupling and zero
compressibility in z for that.
My mdp parameters ar:










*Pcoupl                   = BerendsenPcoupltype            =
semiisotropictau_p                     = 1compressibility       = 4.5e-5
0ref_p                       = 1 1gen_vel                    = nogen_temp
              = 298; options for non-eq viscosity calcdeform = 0 0 0.001 0
0 0refcoord_scaling = com*

Since elongation is in z axis, Lz increases, and Lx and Ly decreases, but
the decrease in these two axis is less compared to increase in Lz, and so
my volume is not conserved, it is increasing.

Can anyone suggest me some way for uniaxial elongation in gromacs, but
volume should not change

Thanks!