[ase-users] Relax unit cell with strain

[James Kermode]

Hi Protik,

ase.constraints.UnitCellFilter has a mask argument that (nearly) does what you need:
https://wiki.fysik.dtu.dk/ase/ase/constraints.html#ase.constraints.UnitCellFilter

For mask you need to pass a 6-element logical array, which specifies which strain components are free to relax, in the Voigt order [eps_xx, eps_yy, eps_zz, eps_yz, eps_xz, eps_xy].  For an orthorhombic crystal mask=[False,False,True,False,False,False] should do what you want.

Best wishes,
James.

> On 11 Jan 2018, at 23:50, Protik Das via ase-users <ase-users at listserv.fysik.dtu.dk> wrote:
> 
> Hi all,
> 
> I need help regarding a cell relaxation problem.
> 
> I would like to strain the structure bi-axially and let the other lattice constant relax. 
> 
> For example, I want to strain lattice vectors a and b. Keep a & b fixed and let the c vector relax. Can it be done using any of the classes from ase.constraints?
> 
> Thanks!
> 
> -- 
> Protik Das,
> ECE Graduate Student,
> LATTE (http://latte.ece.ucr.edu),
> University of California, Riverside.
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