big jumps in E (Re: [Wien] a question on convergence)

[Steven Homolya]

On Mon, 23 Jun 2003, Sergio Galindo Torres wrote:

> I' am working with a 8 atoms primitive cell (7 of Si and 1 of Al). I start a 
> first calculation with 200 k points in the kgen program. After 6 iterations 
> the charge convergence test begin to oscilates as well as the :DIS in the 
> SCF file. So I follow your instruction and set the broyden factor to 0.1 in 
> the case.inm fie. It certanly improve the convergence and the program was 
> able to make 20 iterations without the oscilation. But the oscilation began 
> after that 20 iterations.
> 

When you say oscillate do you mean jump between to a VERY different value? 
If so I'd be interested in possible causes of big jumps (1000s Ry) in 
energy between two values. For me this occurs with a 108 atom system, like 
so:

:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -29584.775822
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -29594.018681
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -55274.088758
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -29618.620985
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -29643.144369
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -55273.997039
:ENE  : *WARNING** TOTAL ENERGY IN Ry =       -29670.361236

One of the numbers, -55274, is reasonable (based on energies of
constituent free atoms). The following warning also appears in the scf
file:

:WARN :      WARNING: Not all eigenvectors are orthogonal

Matrix sizes are 12934, and I'm using the mpi version of the code 
(with NMATMAX=40000). I think scalapack may have been pushed beyond its 
limits.

Any suggestions?

-- 
Steven Homolya
School of Physics and Materials Engineering
Monash University, VIC 3800
Australia
Tel: +61 3 9905 3694
Fax: +61 3 9905 3637