[Pw_forum] strange population analysis result, in PW v 5.4

[Paolo Giannozzi]

In the first case, lattice parameter alat = the value of celldm(1);
in the second case, alat = length of the first cell vector ("a" in
crystallography).
There is a factor sqrt(3) difference.

The "atomic magnetization" (whatever it means) is computed by integrating
over a sphere whose radius is a fixed fraction of the lattice parameter
(look for r_m in the output). So the two magnetizations differ even if
everything else is the same

Paolo



On Sat, Sep 3, 2016 at 5:19 AM, Yi Wang <wangwy13 at gmail.com> wrote:

> Hi, dear developers,
>
> I'm using PW v5.4 to do some calculation, I found the population analysis
> printed during scf calculation has a strange behavior depending on the
> settings of cell_parameter.
>
> bellowing is the input where I found the strange thing:
> as you may see, here, I use celldm(1) and alat to control the cell
> parameters. I got a m=1.36 in this case.
> If I change the cell parameters in the form of "CELL_PARAMETERS bohr", I
> got m=1.96.
> In both cases, the "total magnetization" is 1.96 (the cutoff is not
> converged for the potential, but anyway, potentials and cutoffs are
> irrelevant, I've checked both of them)
> The geometry is essentially the same, but the analysis is very different,
> energy, "total" and "absolute" magnetizations are not affected, of course.
>
> May I also ask is the analysis printed during scf is the Mulliken analysis?
>
>
> &control
>     calculation = 'scf' ,
>     prefix = 'pwscf' ,
>     outdir = './tempfft/' ,
>     pseudo_dir = './' ,
>     restart_mode = from_scratch ,
>     disk_io= 'none'
> /
> &system
>     ibrav = 0 ,
>     ecutwfc = 80 ,
>     occupations = 'tetrahedra' ,
>     nspin=2,
>     nbnd= 18 ,
>     nat = 1 ,
>     ntyp = 1 ,
>     use_all_frac=.TRUE.
>     celldm(1)=2.7120201830,
>     starting_magnetization( 1 )= 0.26,
> /
> &electrons
>     conv_thr = 1d-12 ,
>     diagonalization = 'david' ,
>     mixing_mode = 'plain' ,
>     startingpot = 'atomic' ,
>     startingwfc = 'atomic+random' ,
>     mixing_beta = 0.12 ,
>     mixing_ndim =  10,
> /
> CELL_PARAMETERS alat
> -1 1 1
> 1 -1 1
> 1 1 -1
> ATOMIC_SPECIES
>    Fe 55.845 Fe.gth.upf
> ATOMIC_POSITIONS bohr
> Fe       0 0 0
> K_POINTS automatic
>     20 20 20 0 0 0
>
>
> Thanks for your attention.
>
> Yi Wang
>
> --
> Yi Wang
> Ph.D candidate at Nanjing University of Science and Technology
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>



-- 
Paolo Giannozzi, Dip. Scienze Matematiche Informatiche e Fisiche,
Univ. Udine, via delle Scienze 208, 33100 Udine, Italy
Phone +39-0432-558216, fax +39-0432-558222
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