[QE-users] Monoclinic structure optimization

[Malte Sachs]

Dear Luiz,

from my experience you are using a quite high degauss value of 0.06 for 
a metal. I would guess that for TiNi this value is crucial for the 
distortion. I would try to reduce it to about 0.01 or even 0.005 Ry. 
Moreover, I would recommend to use a marzari-vanderbilt smearing 
compared to the simple gaussian you are using. And as a guess, I think 
you can start your optimization with lower cutoff values (e.g. ecutwfc = 
70 Ry and ecutrho = 560 Ry). This was a safe choice for similar systems 
I have investigated (with the same pseudos).

Best regards,
Maltem

Am 16.06.20 um 17:12 schrieb Luiz Gustavo Davanse da Silveira:
> Dear QE users,
>
> I am trying to optimize NiTi (nitinol) martensite structure (monoclinic,
> space group P21/m) via a vc-relax calculation with cell_dofree = 'ibrav'
> option. The problem is that QE gives me a gamma angle of almost 90° while
> the experimental value is around 97°. I tried to construct an energy vs
> gamma curve keeping the angle fixed and relaxing the axis with cell_dofree
> = 'volume' but it doesn't work since the axis are not orthogonal. I don't
> know what else I can try. If anyone could give me a hint it will be very
> much appreciated.
>
> Find below my input file and the final coordinates outputed by QE.
>
> &CONTROL
>          calculation = 'vc-relax'
>          outdir = './outdir'
>          prefix = 'niti'
>          etot_conv_thr = 1.0E-4
>          pseudo_dir = './pseudo'
>          disk_io = 'none'
> /
> &SYSTEM
>          ibrav = 12
>          A = 2.8
>          B = 4.5
>          C = 4
>          cosAB = -0.1184
>          nat = 4
>          ntyp = 2
>          ecutwfc = 110
>          ecutrho = 1760
>          occupations = 'smearing'
>          degauss = 0.06
>          smearing = 'gauss'
> /
> &ELECTRONS
>          conv_thr = 1.E-8
> /
> &IONS
> /
> &CELL
>          cell_dofree = 'ibrav'
> /
> ATOMIC_SPECIES
> Ni 58.6934 Ni.pbesol-spn-kjpaw_psl.1.0.0.UPF
> Ti 47.867 Ti.pbesol-spn-kjpaw_psl.1.0.0.UPF
> ATOMIC_POSITIONS {crystal}
> Ni 0.9475 0.8070 0.25
> Ni 0.0525 0.1930 0.75
> Ti 0.5274 0.2790 0.25
> Ti 0.4726 0.7210 0.75
> K_POINTS {automatic}
> 14 9 10 0 0 0
>
>
>
> CELL_PARAMETERS (alat=  5.29123317)
>     1.002403137   0.000000000   0.000000000
>    -0.005714828   1.587445555   0.000000000
>     0.000000000   0.000000000   1.513222861
>
> ATOMIC_POSITIONS (crystal)
> Ni            0.9995289657        0.8063481974        0.2500000000
> Ni            0.0004710343        0.1936518026        0.7500000000
> Ti            0.5020451582        0.2794391874        0.2500000000
> Ti            0.4979548418        0.7205608126        0.7500000000
>
>
>
> Best regards,
> Luiz Gustavo D. Silveira
> UFPR - Brazil
>
> _______________________________________________
> Quantum ESPRESSO is supported by MaX (www.max-centre.eu/quantum-espresso)
> users mailing list users at lists.quantum-espresso.org
> https://lists.quantum-espresso.org/mailman/listinfo/users


-- 
Malte Sachs
Anorganische Chemie, Fluorchemie
Philipps-Universität Marburg
Hans-Meerwein-Straße 4
35032 Marburg (Paketpost: 35043 Marburg)
Tel.: +49 (0)6421 28 - 25 68 0
http://www.uni-marburg.de/fb15/ag-kraus/


-------------- next part --------------
A non-text attachment was scrubbed...
Name: smime.p7s
Type: application/pkcs7-signature
Size: 5418 bytes
Desc: S/MIME Cryptographic Signature
URL: <http://lists.quantum-espresso.org/pipermail/users/attachments/20200616/89a5cf3c/attachment.p7s>