The ABINIT Users Mailing List ( CLOSED )

[Xavier Gonze <xavier.gonze@uclouvain.be>]

On 26 Dec 2007, at 17:58, Jess Kondor wrote:

>  Dear all,
>
>    I'm performing convergence tests for the material I am going to  
> study. I use opium generated pseudopotentials. The test on absolute  
> convergence of the total energy shows me that ecut=65 Ry is  
> appropriate value (error on total energy is < 5meV/atom). But I am  
> primary interested in other properties (lattice parameters,  
> electric polarization, etc) rather than total energy. So, I tested  
> those properties vs ecut (from 40 through 70 Ry).  I found that  
> those properties are in very good agreement with available data  
> starting from Ecut = 45 Ry (except one thing - the pressure at low  
> Ecut is very high ~25-70 GPa, and at 70 Ry pressure < 0.01 GPa).

Concerning the latter, do you use ecutsm ?

> So, I am wondering which ecut I should use in my further  
> calculations. I am going to study surfaces of my material.
You can likely explore your system with 45 Ry, then ... come back to  
a convergence study
for the properties of the surface that you care about. Convergence  
tests should
be done on the property you are interested in.

X.