[Pw_forum] Choice of cutoff (was: Pw_forum Digest, Vol 40, Issue 20)

[Paolo Giannozzi]

On Oct 14, 2010, at 21:14 , Tram Bui wrote:

>   My name is Tram Bui and i'm new to the forum so i'm not quite  
> sure how the Q&A work

definitely so: you have already violated a number of basic rules,  
such as
- choose a meaningful subject
- do not use "reply" to start a new thread: it will confuse the  
ordering of messages into threads
- do not use "reply" with a Digest!!!
- do not quote a bunch of irrelevant stuff in your reply

> how do you determine (or find) the ecutoff (kinetic energy cutoff  
> of wave function)
> value for a material structure such as SiC?

the answer is left as an exercise to the reader. Really: you have to  
decide a
convergence criterion on some physical property, then verify which  
cutoff
gives you a converged answer. As a rule, it depends a lot upon  
pseudopotentials

For more: http://www.quantum-espresso.org/learn.php

P.
---
Paolo Giannozzi, Dept of Chemistry&Physics, Univ. Udine
via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222