[Pw_forum] about the number of bands

[Alcantara Ortigoza, Marisol]

Dear all,
 
I understand that to solve the eigenvalue problem one uses the available subroutines to diagonalize the Hamiltonian matrix and usually, for convinience, we request to find only the lowest eigenvectors (occupied plus a few unoccupied bands). However, is there any reason why increasing the number of eigenvalues (bands) to be computed improves or speeds the convergence of these, curing the warnings saying that such and such eigenvectors did not convege (usually the highest ones, I read in the forum)? 
 
Thank you very much.
Marisol
 
...................................................................................................................
Marisol Alcántara Ortigoza   Phone: + (407) 823 1543,  Fax: +(407) 823-5112 Cel + (407) 844 3052

Kansas State University  
116 Cardwell Hall    
Manhattan, Kansas 66506, USA
 
University of Central Florida
4000 Central Florida Boulevard
Building 12 Room 418
Orlando, Florida 32816-2385 
 

________________________________

From: pw_forum-admin at pwscf.org on behalf of Paolo Giannozzi
Sent: Sat 6/16/2007 12:48 PM
To: pw_forum at pwscf.org
Subject: Re: [Pw_forum] nscf error




On Jun 16, 2007, at 15:12 , Hashem Al-Yamani wrote:

> While doing a nscf calculation  in order to plot PDOS for IrO2 by 
> using
> K_POINTS [automatic] option, it gave the following error :
> [...]
> from efermit : error # 1
> unexpected error

did you specify enough bands?

Paolo
---
Paolo Giannozzi, Democritos and University of Udine, Italy


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