[gpaw-users] different convergence properties depending on LCAO guess

[Ask Hjorth Larsen]

Hi Nick

On Mon, 26 Jul 2010, naromero at alcf.anl.gov wrote:

> Hi,
>
> I have a system where the LCAO guess leads to very different behavior in the
> SCF cycle. This is even with a small mixing parameter of ~ 0.01:
>
> 1. basis = 'sz' appears to converge the system, albeit very slowly
> 2. basis = partial wave expansions causes the system to jump suddenly from a negative energy to a positive energy (after iter: 3) and eventually fail due to inability to locate the Fermi energy.

It sounds like a case where the real problem might be a too low number of 
bands, which can really throw the rmm-diis eigensolver off - try 
increasing nbands.  How many bands and electrons, and what temperature are 
you using?

>
> The system is an interface between a semi-conductor and a semi-metal. 
> Are there any particular family of systems that can be very sensitive to 
> the details of the LCAO initialization?

Nothing in particular that I know of - but let's see if the above works 
before we start worrying too much.

Regards
Ask