[DFTB-Plus-User] Correct handling of lattice parameters (Monoclinic, Tetragonal)

[Husak Michal]

Sorry for missprint:
Monoclinic = lattice parameter beta should be free, only alpha and gamma fixed to 90 degree.
There is no setup for this behaviour in DFBT+ ...
Michal
________________________________
From: DFTB-Plus-User <dftb-plus-user-bounces at mailman.zfn.uni-bremen.de> on behalf of Husak Michal via DFTB-Plus-User <dftb-plus-user at mailman.zfn.uni-bremen.de>
Sent: Saturday, October 12, 2024 5:37:22 PM
To: dftb-plus-user at mailman.zfn.uni-bremen.de
Cc: Husak Michal
Subject: [DFTB-Plus-User] Correct handling of lattice parameters (Monoclinic, Tetragonal)

I see my previous E-mail was added to incorrect thread ...


Question:

How to handle correctly in DFTB+ crystals with a lattice with given lattice parameters restriction (when the cell is optimized).

Examples:

Monoclinic = parameter beta needs to be fixed to 90

Tetragonal = a should be equal to b

e.t.c.


Current version of DFBT+ makes possible only to fix ALL angles , not each one individually ...

It does not make possible to give expression between lattice vectors length (e.g. a=b) as well ...


Without this future calculation of crystals with known crystal system can not be done correctly ...


Michal Husak

UCT Prague


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