[Wien] Ce does not converge

[Tran, Fabien]

Maybe you already know our paper (see appendix):
https://journals.aps.org/prb/abstract/10.1103/PhysRevB.89.155106


________________________________________
From: Wien <wien-bounces at zeus.theochem.tuwien.ac.at> on behalf of Peter Blaha <pblaha at theochem.tuwien.ac.at>
Sent: Wednesday, January 29, 2020 6:13 PM
To: wien at zeus.theochem.tuwien.ac.at
Subject: Re: [Wien] Ce does not converge

A "lanthanide" is NEVER simple.

The 4f states in GGA are all at EF and form a very narrow band. Thus
tiny changes in the potential move the 4f states relative to the broad
s,d states and huge internal charge transfer can occur.

RKmax=7 for a 4f element is MUCH too small. Use at least  8, better 9-10

Use TEMP(S) with 6 mRy (at the beginning). It damps oszillations.

Use a good k-mesh. 1000 k-points are by a factor of 10 too small.

I'm not sure if GGA+U is very good for Ce metal, at least not for the
low-volume fcc phase.

Am 29.01.2020 um 17:26 schrieb delamora:
> Dear WIEN2k community;
> I tried to make a spin polarized calculation the Ce metal;
> FCC a=b=c=5.16A with a U=5eV
> and also an antiferromagnetic calculation
> a=b=c/sqrt(2), c=5.16A
> Ce up; 0,0,0
> Ce dn; 1/2, 1/2, 1/2
> and they did not converge with cc=0.001
>
> for the ferromagnetic calculation I did 140 iterations with RxK=7 and
> #K=10,000
> :ENERGY convergence:  0 0 .0000693950000000
> :ENERGY convergence:  0 0 .0001091800000000
> :ENERGY convergence:  0 0 .0002001000000000
> :DIS  :  CHARGE DISTANCE       ( 0.0377909 for atom    1 spin 1)
>   0.0820411
> :DIS  :  CHARGE DISTANCE       ( 0.0301614 for atom    1 spin 1)
>   0.0685493
> :DIS  :  CHARGE DISTANCE       ( 0.0278653 for atom    1 spin 1)
>   0.0641289
>
> for the antiferromagnetic calculation I had RxK=7 and #K=1,000 and I did
> 63 iterations
>
> I find confusing that a simple calculation for a lanthanide element does
> not converge.
>
> Pablo
>
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