[QE-users] Help: How to optimise lattice c parameter in scf calculation

[Pietro Delugas]

other issue is that  celldm(3) is the ratio between c axis length and 
celldm(1), thus  you should consider values for celldm(3)  between 
10./celldm(1) and 16/celldm(1).



On 17/11/18 04:08, Yun Wang wrote:
>
> Dear Edmund,
>
>
> The (1x1x1) k-point mesh is not good enough to get the reliable data 
> for your system.
>
>
> You may also need to consider the van der Waals correction due to the 
> existence of the large atoms.
>
>
> Best regards,
>
> Yun
>
>
> *Dr Yun Wang | Senior Lecturer PhD*
> *Centre for Clean Environment and Energy | **School of Environment & 
> Science*
> *Griffith University****| Gold Coast campus | QLD 4215 | G24 Room 3.36*
> *T +61 7 5552 8358 |  email **yun.wang at griffith.edu.au* 
> <mailto:yun.wang at griffith.edu.au>
> https://experts.griffith.edu.au/academic/yun.wang
>
> Griffith University - CRICOS Provider Number 00233E
> PRIVILEGED - PRIVATE AND CONFIDENTIAL
> ------------------------------------------------------------------------
> *From:* users <users-bounces at lists.quantum-espresso.org> on behalf of 
> Chan, Edmund <thc208 at exeter.ac.uk>
> *Sent:* Saturday, November 17, 2018 8:40:02 AM
> *To:* users at lists.quantum-espresso.org
> *Subject:* [QE-users] Help: How to optimise lattice c parameter in scf 
> calculation
>
> Dear all,
>
> I am currently working on a CH3NH3PbI3 I4/mcm tetragonal structure. I 
> would like to optimise the lattice parameter c using scf calculation 
> after optimising geometry using relax calculation. I tried to fix 
> celldm(1) and changes celldm(3) so that lattice parameter c ranges 
> 10.5-13.5 (true value should be about 12.6, sum of Pb-I-Pb-I-Pb) 
> However, calculations still don't show min energy within the range. 
> still decreasing when celldm(3) keeps decreasing.
>
> Any solution?
>
> Thanks a lot in advance.
>
> #!/bin/sh
>
> ####################################################################
>
> #
>
> # define the following variables according to your needs
>
> #
>
> # outdir=temporary_directory_for_large_files
>
> # pseudo_dir=directory_where_pp-files_are_kept
>
> # espresso_dir=top_directory_of_espresso_package
>
> # code : sh run_si_eos
>
> ####################################################################
>
> rm -f MAPI_scf.out MAPI.etot_vs_alat
>
> touch MAPI.etot_vs_alat
>
> for alat in 1.2572090494 1.2721758238 1.2871425982 1.3021093726 
> 1.317076147 1.3320429214 1.3470096958 1.3619764701 1.3769432445 
> 1.3919100189 1.4068767933 1.4218435677 1.4368103421 1.4517771165 
> 1.4667438909 1.4817106653 1.4966774397 ; do
>
> # self-consistent calculation
>
> cat > MAPI_scf.in << EOF
>
> &control
>
> calculation='scf',
>
> restart_mode='from_scratch',
>
> prefix='MAPI',
>
> pseudo_dir = '/home/edmund/Quantum-Espresso/pseudo/SSSP_Acc/PBESOL/',
>
> outdir='/home/edmund/Quantum-Espresso/Tutorial/tmp/'
>
> /
>
> &system
>
> ibrav= 6, celldm(1) = 16.703665958 , celldm(3) = $alat , nat= 12, ntyp= 5,
>
> ecutwfc = 70,
>
> /
>
> &electrons
>
> electron_maxstep = 5000,
>
> mixing_beta = 0.3,
>
> conv_thr = 1.0d-6,
>
> /
>
> &ions
>
> ion_dynamics="bfgs",
>
> /
>
> ATOMIC_SPECIES
>
> C 12.01070 c_pbesol_v1.2.uspp.F.UPF
>
> H 1.00794 H.pbesol-rrkjus_psl.0.1.UPF
>
> N 14.00670 N.pbesol-theos.UPF
>
> Pb 207.20000 Pb.pbesol-dn-kjpaw_psl.0.2.2.UPF
>
> I 126.90450 i_pbesol_v1.uspp.F.UPF
>
> ATOMIC_POSITIONS (alat)
>
> Pb -0.060250864 0.119717291 0.415558090
>
> I -0.007273724 -0.001439398 0.113823814
>
> I 0.267082396 0.174145023 0.503051646
>
> I -0.111188287 -0.164962141 0.584095713
>
> C 0.535192046 0.927588487 0.796494424
>
> H 0.581905016 1.042275920 0.809533204
>
> H 0.580744698 0.877063608 0.692556190
>
> H 0.570638845 0.855097719 0.891131917
>
> N 0.366943691 0.939129847 0.789578969
>
> H 0.318073687 0.834961464 0.773620510
>
> H 0.328759438 1.011781981 0.698437223
>
> H 0.325773058 0.986440200 0.887518302
>
> K_POINTS automatic
>
> 1 1 1 0 0 0
>
> EOF
>
> pw.x < MAPI_scf.in > MAPI_scf.out
>
> # extract Etot from output
>
> etot=`grep -e ! MAPI_scf.out | awk '{print $(NF-1)}'`
>
> echo $alat $etot >> MAPI.etot_vs_alat
>
> done
>
> Kind regards,
>
> Edmund Chan
>
> ________________________________________________
>
> *Edmund Chan*
>
> PhD Renewable Energy Student
>
> Environment & Sustainablity Institute
>
> College of Engineering, Mathematics and Physical Sciences
>
> University of Exeter, Penryn Campus
>
> Penryn, Cornwall
>
> United Kingdom
>
> TR10 9FE
>
>
> /Tel:/+44 (0)7455 235 701
>
> /Email:/thc208 at exeter.ac.uk <mailto:thc208 at exeter.ac.uk>
>
> /LinkedIn: https://uk.linkedin.com/in/edmundchan1///
>
> uoe//
>
> cid:image002.gif at 01D2F1A2.9AF74CE0
>
>
> _______________________________________________
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