[Pw_forum] fixing the angle.

[Lorenzo Paulatto]

In data 02 novembre 2009 alle ore 09:15:06, Bipul Rakshit
<bipulrr at gmail.com> ha scritto:
> What I want is to optimise the structure, using vc-relax. Beside I also
> want that, the angle should not change between the atoms and vc-relax
give me
> an optimised structure.

Dear Bipul,
it's not very clear to me which angle do you want to keep fixed, but it
doesn't really matter.

You can nail the atoms to their initial positions setting the additional
flags in the atomic position lines; this will work if you are using
crystal or alat coordinates (you are), it will only allow the cell volume
to change.

Otherwise you can set a constrain, you can find the documentation in
Doc/INPUT_PW.txt. It is not difficult at all, but it does not work with
bfgs, so you'll have to use damp dynamics for the atoms relaxation.

best regards

-- 
Lorenzo Paulatto
SISSA  &  DEMOCRITOS (Trieste)
phone: +39 040 3787 511
skype: paulatz
www:   http://people.sissa.it/~paulatto/

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