[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

-Original Message- From: wien-boun...@zeus.theochem.tuwien.ac.at [mailto:wien-bounces at zeus.theochem.tuwien.ac.at] On Behalf Of Stefaan Cottenier Sent: Monday, February 22, 2010 1:30 PM To: A Mailing list for WIEN2k users Subject: Re: [Wien] [Wien2k User Group] Lattice stability in

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

Dear Stefaan, Thanks for the reply. Let me explain my position. Let us take an example of uranium. The stable phases of uranium are C-centered orthorhombic (alpha), primitive tetragonal(beta) and fcc (gamma). Getting the atomic positions of these phases from ICSD, I can calculate the ENE

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

We consider that the stable ground state of a metal is bcc. The fcc structure is the high temperature phase. To calculate the enthalpy of transformation of the fcc to bcc, we consider the following Enthalpy of transformation =ENE(fcc)-ENE(bcc) Now for this above equation, do we have to

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

Is there any way out to simultaneously optimize the lattice parameters and the internal coordinates in w2web? You might read the structure optimization notes at http://www.wien2k.at/reg_user/textbooks/ (in particular Sec. 5) Stefaan

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

Hi Stefaan, I now noticed the following comment in your reply Yes (geometry optimization for bcc or fcc = find the optimal lattice constant, no troubles here with internal coordinates). You have mentioned fcc or bcc. Why or? I ask this question from the point of view of uranium allotropes.

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

Thanks Stefaan, 1. I want optimized positions in case of experimentally known crystal structures. Does it really help? Is it worth doing? I may be wrong or may be doing what is not required. 2. I want to do only internal coordinates optimization for metastable phases. Is it incomplete?

[Wien] [Wien2k User Group] Lattice stability in bcc, fcc and hcp and other crystal structures

1. I want optimized positions in case of experimentally known crystal structures. Does it really help? Is it worth doing? I may be wrong or may be doing what is not required. 2. I want to do only internal coordinates optimization for metastable phases. Is it incomplete? It all depends