[Pw_forum] fixed spin moment calculation

Thu Mar 12 13:43:42 CET 2009

Dear Yumin Qian,
You may want to check with another pseudopotential for Oxygen. It might be totally unrelated but I've seen this attached in the details part:
Warning: this O psp has been tested in liquid water simulations by 
Patrick Sit and Nicola Marzari. Results for the diffusion coefficient
and pair correlation functions were at odd with those obtained with 
other ultrasoft or norm-conserving pseudopotentials, and recently
published result.
Emine Kucukbenli, grad student, SISSA, Italy.

--- On Thu, 3/12/09, yumin qian <yuminqian at gmail.com> wrote:
From: yumin qian <yuminqian at gmail.com>
Subject: Re: [Pw_forum] fixed spin moment calculation
To: "PWSCF Forum" <pw_forum at pwscf.org>
Date: Thursday, March 12, 2009, 1:01 PM

Sorry for confuse you ,  After checking the input and output file , I found that I also did  a LiVO2 crystal calcualtion with the same problem, the input file I posted is for LiNiO2 and the output file I posted  is for LiVO2  , here is the complete input and output file from the same calcualtion

&control
    calculation='scf'
    restart_mode='from_scratch' ,
    pseudo_dir = '~/software/espresso-4test/pseudo',
    outdir='outscf'
    nstep=60
    prefix='AFM-type'

    tstress = .true.
    tprnfor = .true.
    wf_collect=.true.
 /
 &system
    ibrav = 0, nat=16 , ntyp= 4,
    ecutwfc = 35.0, ecutrho = 300.0,
    occupations='tetrahedra',
    nspin=2,constrained_magnetization='atomic',lambda=5.0,

starting_magnetization(1)= 0.0,
starting_magnetization(2)= 1.8,
starting_magnetization(3)=-1.8,
starting_magnetization(4)= 0.0,
lda_plus_u=.true.
Hubbard_U(1)=0.0
Hubbard_U(2)=3.0
Hubbard_U(3)=3.0

Hubbard_U(4)=0.0

 /
 &electrons
    diagonalization='david',
    conv_thr = 1.0e-7,
    mixing_beta = 0.5,
 /

ATOMIC_SPECIES
Li    6.914      Li.pbe-n-mt_bw.UPF
V1  50.9415   V.pbe-n-van.UPF

V2  50.9415   V.pbe-n-van.UPF
O   15.9994   O.pbe-van_bm.UPF
ATOMIC_POSITIONS {crystal}
Li  0.0000000000000000  0.0000000000000000  0.0
Li  0.0000000000000000  0.0000000000000000  0.5
Li  0.5000000000000000  0.5000000000000000  0.0

Li  0.5000000000000000  0.5000000000000000  0.5
V1  0.0000000000000000  0.5000000000000000  0.25
V2  0.0000000000000000  0.5000000000000000  0.75
V2  0.5000000000000000  0.0000000000000000  0.25
V1  0.5000000000000000  0.0000000000000000  0.75

O   0.2354848230051515  0.0000000000000000  0.35287967
O   0.2354848230051515  0.0000000000000000  0.85287967
O   0.7354848230051516  0.5000000000000000  0.35287967
O   0.7354848230051516  0.5000000000000000  0.85287967

O   0.7645151769948484  0.0000000000000000  0.14712033
O   0.7645151769948484  0.0000000000000000  0.64712033
O   0.2645151769948484  0.5000000000000000  0.14712033
O   0.2645151769948484  0.5000000000000000  0.64712033

K_POINTS {automatic}
  8 8 6  1 1 1
CELL_PARAMETERS (alat)
    9.903876    0.000000    0.000000
    0.000000    5.622988    0.000000
   -6.542514    0.000000   20.135790

the output file gives 

 ==============================================================================
     atom number    4 relative position :    0.1697   0.2839   1.0166
     charge :     0.065485
     magnetization :          0.000000

     magnetization/charge:    0.000000
     constrained moment :     0.000000

 ==============================================================================

 ==============================================================================

     atom number    5 relative position :   -0.1652   0.2839   0.5083
     charge :     2.371448
     magnetization :          1.554551
     magnetization/charge:    0.655528
     constrained moment :     1.800000

I also  changed lambda from 1 to 5 and the   final magnetic moment changed from 1.55 to 1.50 
so the parameter lambda seems  have no impact on the final magnetic moment, there should be something wrong with my calcualtion but I can't spot this error. 

2009/3/12 Gabriele Sclauzero <sclauzer at sissa.it>

Dear Yumin Qian,

   There's something strange in this output. I think that atom number 5 should be a Ni

one, since you were interested in the magnetization of that species, but then, why is the
charge around that atom only about 2.5? Ni should have 10 electrons in valence, so I would
expect to get a number around 10 for the charge (unless the atom goes in a very ionized

state, but that seems highly unprobable to me).
Are you sure PPs and all the rest is OK?

GS

yumin qian wrote:
> thanks for your reply ,I  changed the lambda=5.0 and used
>    occupations='tetrahedra'  but the magnetization still did not
> converge to the initial value ,but the total energy converged.

> I do know what is the problem.

>      ==============================================================================
>      >      atom number    5 relative position :   -0.1652   0.2839   0.5083
>      >      charge :     2.373353

>      >      magnetization :          1.544423
>      >      magnetization/charge:    0.650735
>      >      constrained moment :     1.800000
>      >
>      >
>      ==============================================================================

>      > the output file gives a magnetic moment of 1.5444 ,how should I do to
>      > make the calculation  converge to the starting_magnetization 1.8 ?
>

--

o ------------------------------------------------ o
| Gabriele Sclauzero, PhD Student                  |
| c/o:   SISSA & CNR-INFM Democritos,              |
|        via Beirut 2-4, 34014 Trieste (Italy)     |

| email: sclauzer at sissa.it                         |
| phone: +39 040 3787 511                          |
| skype: gurlonotturno                             |
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-- 
Sincerely Y. M. Qian 
Lab.of Condensed Matter Theory and Materials Computation 
Institute of Physics 
Chinese Academy of Sciences
Tel:  + 8610 8264 9147

E-Mail:yuminqian at gmail.com 
P.O.Box 603   Beijing 100190
China 

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