Pressure effect

[Steven]

hello Sir
      By applying different pressure on a crystal structure i have calculated different Enthalpies at those pressure(Using OptimizeGeometry Block). I am getting a linear response upto a certain pressure(which is correct) but after that it is becoming zig zag.How can i rectify the problem? I am using the same Density cut-off and k-pts

[Jess Wellendorff]

It is not clear to me if this is a software problem (wrong results) or a scientific problem (what should the behavior actually be?)

[Steven]

Ok sir i got the answer .
     Thank you