[Wien] symmetry problem for spontaneous polarization

[Fecher, Gerhard]

you need first to initialize the "low symmetry" structure with the displaced atom(s),
and afterwards run the "high" symmetry structure with the atoms placed back (do not accept symmetry changes during initialisation). 

Ciao
Gerhard

DEEP THOUGHT in D. Adams; Hitchhikers Guide to the Galaxy:
"I think the problem, to be quite honest with you,
is that you have never actually known what the question is."

====================================
Dr. Gerhard H. Fecher
Institut of Inorganic and Analytical Chemistry
Johannes Gutenberg - University
55099 Mainz
and
Max Planck Institute for Chemical Physics of Solids
01187 Dresden
________________________________________
Von: Wien [wien-bounces at zeus.theochem.tuwien.ac.at] im Auftrag von Jameela Fatheema [j.fatheema96 at yahoo.com]
Gesendet: Montag, 17. Juli 2017 10:11
An: A. Mailing List for WIEN2k Users
Betreff: [Wien] symmetry problem for spontaneous polarization

Dear all,

I am running wien version 14 on ubuntu 16.

The purpose of my calculations is to calculate the spontaneous polarization for Bi4Ti3O12 tetragonal structure.

I have followed the steps provided by the wien2k UG and the notes that are available on wien2k site. The space group is I4/mmm which genertaes 16 symmetry operations for the structure. For the noncentrosymmetric polarization, i displace the titanium and oxygen atoms in the z-direction, about 0.005. this changes the symmetry to 8 and i get the space group as I4mm. After the total polarization for I4mm is obtained i do the steps as mentioned in the notes and tutorial available. The problem is how do i avoid this symmetry change because as much i understand the symmetry needs to remain the same. If i dont do the initialization for the centrosyymetric calculations it shows the ROTDEF error in dstart which is due to the symmetry difference.

Should i make the displacement even more smaller?

I will be very thankful for any advice.

Regards
Jameela Fatheema
University of Peshawar.