[Pw_forum] Calculating stable lattice parameter for non-cubic structure

[efi dwi indari]

Dear All,

I am now on my way in determining stable lattice parameter of both
orthorhombic and tetragonal structures. Previously everything was going
well when I calculated the cubic one as I obtained the U-curve from which I
got the value of stable lattice parameter which corresponds to the lowest
total energy.

Yet, when I move forward to the orthorhombic and tetragonal ones and when I
varied one of the lattice parameters (while the other(s) remains constant),
I could not obtain the U-curve. Instead, I got a linear curve, with lower
total energy as I go to smaller lattice parameter. Does anyone have any
idea how to deal with this issue? I have already googled but unfortunately
not yet found any solution.

Any help would be really appreciated. Thank you in advance.

Best Regards,

Efi Dwi Indari
Research assistant, Bandung Institute of Technology
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