[Wien] lapwdm with ROOT option in case.in2

[Pavel Novak]

Dear Masao Arai,

your result is in fact not too surprising. ROOT option simply fill the
electron states until the number of electrons is exhausted. If for the
last electron there are several degenerate states available, it puts in
each of these states equal fraction of the electron. TETRA procceds
differently and thus ROOT and TETRA may well finish with different
distribution of electrons that are close to the Fermi energy. LDA+U then
basicaly stabilize the states that are occupied and destabilize empty
states. Different state may therefore be stabilized with TETRA and with
ROOT. The best you can do is to construct different starting population
matrices and to run LDA+U several times (with the same option either TETRA
or ROOT). Etot then decides which of the solutions corresponds to the
ground state.

Regards
Pavel

_________________________________________________
Dr. Pavel Novak
Department of Magnetism and Superconductivity
Institute of Physics AS CR
Cukrovarnicka 10, 162 53 Praha 6, Czech Republic
tel: +420 2 20 318 532
e-mail: novakp at fzu.cz

On Thu, 28 Jun 2007, Masao ARAI wrote:

> Dear WIEN2k users and depelopers,
>
> I have experienced a strange problem about LSDA+U calculation
> with ROOT option in case.in2. Is the ROOT option compatible with
> lapwdm?
>
> Let me explain the situation.
>
> (1) First, I performed standard LSDA+U calculations with
> "TETRA" option in case.in2.
> I obtained well converged insulating ground state.
>
> (2) I modified the case.in2 and set "ROOT" option. Then I restarded
> the LSDA+U calculations with converged charge density and case.dmat* files.
> However, the calculuation was converged to the completely different state.
> At the first iteration, the eigenvalue agreed with those from (1). But, the
> density matrices computed from lapwdm were different from those in (1).
>
> I suspect that the lapwdm is not compatible with ROOT option.
>
> The lapw2 emits weights to case.weighdn and case.weighup. These weights
> are then read by lapwdm. When the ROOT option is used, the weights
> emitted by
> lapw2  are just proportinal to the multiplicities of k-points.
> Even states higher than Fermi energy have non zero weights in case.weighdn
> and case.weighup.
>
> Note, the weights in case.weightup/dn (file no.11) are
> appropriately truncated at EF and the weights of states with higher
> energy are zero.(around line 455-462 in lapw2.F)
>
> 455            DO IE=1,NE(K)
> 456                wei=WEIGH(k,ie)
> 457                eee= E(k+(ie-1)*2*nkpt)
> 458                IF (eee.lt.eeeo) shift=0.
> 459                eeeo=eee
> 460                eee=eee+shift
> 461                IF (eee.gt.EF) wei=0.
> 462                WRITE(11,79) eee,wei
> 463            END DO
>
>
> But, the weights in case.weighup (file no.26)and case.weighdn (no.27)
> are emitted without any special treatment. (line 333 and 351 in lapw2.F)
>
> 333                   write(26)(WEIGH(J,N), N=1,NE(J))
> 351                      write(27)(WEIGH(J,N), N=1,NE(J))
>
>
> Of course, the states higer than EF will not be used in lapw2 because
> the varibale nemax is appropriately adjusted.
>
> In lapwdm, the weights are read from case.weighdn/up.
> Then all states are used for computation of the density matrices.
> (There is no trick like nemax in lapw2). So, if the ROOT option is used,
> the lapwdm seems to give wrong values.
>
> Your sincerely,
>
> --
> Masao Arai
> NIMS(National Institute for Materials Science)
> CMSC(Computational Materials Science Center)
> Tsukuba Japan
>
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