[Pw_forum] about C2/c point group symmetry of a monoclinic lattice.

Mutlu COLAKOGULLARI mutlucolakogullari at trakya.edu.tr
Thu Dec 18 20:29:04 CET 2014

Dear Carlo, Andrea and Paolo;
	The taking responds and advices from people who has experienced makes me happy.
	As Paolo and Carlo also said, cif2qe.sh is not working properly, (at least for this case). Therefore, I used the other codes for double cross check: pymatgen and cif2cell. The conventional cell has 64 atoms whereas its primitive has 32 atoms. 
	Pymatgen is very proper for POSCAR output because it takes symmetry analysis depend on Curtarolo-Setyawan's paper [http://arxiv.org/abs/1004.2974v1] (MCLC5 - it gives also gamma angle, for this case)...so, it is not matching with QE's ibrav settings depend on cell vectors. Cif2Cell code gives the exactly same CELL_PARAMETERS card with Quantum-ESPRESSO's ibrav=-13...that is the reason why I chose Cif2Cell code.
	Andrea, it was my fault. I had been complicated among space groups(2/m for sg:12 and 2/C for sg:15) and Herman-Mauguin notations(2/m for space groups 12-15). You said that ”Using ibrav=-13 it is not necessary to add these atoms in the list of atoms inside the unit cell." Andrea, you mean that could I decrease the number of atoms in primitive cell if they have symmetrized by last 4 symmetry operations in this case? By this way, the cell lost half of atoms inside which is good news for computational resources. 
	With my best wishes,

------------------------------------------Dr. Mutlu COLAKOGULLARITrakya Universitesi Fen FakultesiFizik Bolumu22030 Merkez-EDİRNE
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