[Pw_forum] VC-relax collapsing unit cell

[John Bilgerman]

Thanks for the tip. I'd only tried up to about a hundred in my tests, I'll
start looking even higher. I attempted this over the weekend on my (old!)
desktop, but found I will have to wait a week or two until I get cluster
access before I can check and see if it was the only issue.

Thanks,
John

On Sat, Nov 19, 2016 at 2:34 AM, Paolo Giannozzi <p.giannozzi at gmail.com>
wrote:

> Not sure this is the (only) problem, but 35 Ry for norm-conserving Iron
> with semicore states is way too small. 200-300 Ry is a more appropriate
> cutoff.
>
> Paolo
>
> On Sat, Nov 19, 2016 at 12:25 AM, John Bilgerman <bilgermanjohn at gmail.com>
> wrote:
>
>> Hi,
>>
>> I've been banging my head against this and cannot find what is likely a
>> silly mistake despite many tests and lots of reading.
>>
>> I'm trying to optimize the (known) structure of NaFePO4 as a test. I'm
>> starting from the experimental crystal structure, so the drastic collapse
>> of the unit cell to < 1/2 suggests an issue.
>>
>> I know the common problem is inputing the structure wrong, but I've done
>> my best (and sanity-checked the input/output files with Xcrysden).
>>
>> I'm new to QE, any help would be appreciated.
>>
>> Input file:
>>  &CONTROL
>>                  calculation = 'vc-relax' ,
>>                 restart_mode = 'from_scratch' ,
>>                       outdir = './' ,
>>                       wfcdir = './scratch' ,
>>                   pseudo_dir = './pseudo' ,
>>                      disk_io = 'default' ,
>>                    verbosity = 'high' ,
>>  /
>>  &SYSTEM
>>                        ibrav = 8,
>>                  space_group = 62 ,
>>                            A = 9.001 ,
>>                            B = 6.874 ,
>>                            C = 5.052 ,
>>                        cosAB = 0 ,
>>                        cosAC = 0 ,
>>                        cosBC = 0 ,
>>                          nat = 6,
>>                         ntyp = 4,
>>                      ecutwfc = 35 ,
>>                      ecutrho = 140 ,
>>                  occupations = 'smearing' ,
>>                      degauss = 0.02 ,
>>                     smearing = 'gaussian' ,
>>                        nspin = 2 ,
>>    starting_magnetization(1) = 0.7,
>>    starting_magnetization(2) = 0,
>>    starting_magnetization(3) = 0,
>>    starting_magnetization(4) = 0,
>>                     noncolin = .false. ,
>>  /
>>  &ELECTRONS
>>              diagonalization = 'david' ,
>>  /
>>  &IONS
>>  /
>>  &CELL
>>  /
>> ATOMIC_SPECIES
>>    Fe   55.00000  Fe.pbe-sp-hgh.upf
>>     P   30.00000  P.pbe-hgh.upf
>>    Na   22.00000  Na.pbe-sp-hgh.upf
>>     O   16.00000  O.pbe-hgh.upf
>> ATOMIC_POSITIONS crystal_sg
>> Fe 4a
>> P 4c 0.17585  0.46447
>> Na 4c  0.34999  0.9702
>> O 8d 0.1212 0.0682 0.3177
>> O 8d 0.3486 0.25 0.4561
>> O 8d 0.1154 0.25 0.7507
>> K_POINTS automatic
>>   2 3 4   1 1 1
>>
>>
>> The relevant parts of the CIF file for the structure are:
>> ...
>> _cell_length_a 9.001(8)
>> _cell_length_b 6.874(3)
>> _cell_length_c 5.052(4)
>> _cell_angle_alpha 90.
>> _cell_angle_beta 90.
>> _cell_angle_gamma 90.
>> _cell_volume 312.58
>> _cell_formula_units_Z 4
>> _symmetry_space_group_name_H-M 'P n m a'
>> _symmetry_Int_Tables_number 62
>> ...
>> Fe1 Fe2+ 4 a 0 0 0 . 1. 0
>> P1 P5+ 4 c 0.17585(4) 0.25 0.46447(8) . 1. 0
>> Na1 Na1+ 4 c 0.34999(9) 0.25 0.9702(2) . 1. 0
>> O1 O2- 8 d 0.1212(1) 0.0682(1) 0.3177(2) . 1. 0
>> O2 O2- 4 c 0.3486(1) 0.25 0.4561(2) . 1. 0
>> O3 O2- 4 c 0.1154(1) 0.25 0.7507(2) . 1. 0
>> ...
>>
>> John
>>
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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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>
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