[Pw_forum] about total magnetization convergence

Nicola Marzari marzari at MIT.EDU
Thu Jun 15 20:05:08 CEST 2006

One possibility is that you are converging to different self-consistent
states - in a spin-polarized calculation this is fairly common - and the
energy differences between different magnetizations could be small.

So, what you are seeing might not be an erratic behavior, but the fact
that there are two or more potential energy surfaces very close to each
other, and corresponding to different magnetizations.

As always, check carefully k-point sampling and the amount of degauss
used (around 0.01-0.02 Ry, for this case). Note that you can fix the tot
amgnetization in the code, if needed.


aarti srirangarajan wrote:
> Dear all,
> I am doing a spin polarised slab calculation with vacuum layers for Ni.
> I have a problem here with the total magnetization values. I hv performed
> calculations with 7 7 1 , 9 9 1 and 11 11 1 and 13 13 1 k-point meshes for
> various surfaces  and
> the total magnetisation changes very erratically. The values are not
> converging. Although the Final energies are converging very well.
> Also the difference b/w the Total and abs. magnetisation is of the order
> of 2 bohrs. Could anyone help me with this?
> thank you
> Aarti
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Prof Nicola Marzari   Department of Materials Science and Engineering
13-5066   MIT   77 Massachusetts Avenue   Cambridge MA 02139-4307 USA
tel 617.4522758 fax 2586534 marzari at mit.edu http://quasiamore.mit.edu

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