Dear all users, I am currently trying to relax a methylammonium lead iodide CH3NH3PbI3 structure which has tetragonal structure I4/mcm. Thus, in my input file, I select ibrav = 7 (body centred teragonal). However, as I visualise the input and output on Xcrysden, the unit cell becomes orthorhombic. Why is that?
&CONTROL title = 'MAPI' , calculation = 'relax' , restart_mode = 'from_scratch' , outdir = './' , pseudo_dir = './' , prefix = 'CH3NH3PbI3' , / &SYSTEM ibrav = 7, A = 8.83920, C = 12.6948, nat = 12, ntyp = 5, ecutwfc = 80 , ecutrho = 800, / &ELECTRONS electron_maxstep = 5000 , conv_thr = 1.0d-6 , mixing_beta = 0.3 , / &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 0.000000000 0.000000000 0.500000000 I 0.000000000 0.000000000 0.250000000 I 0.294200000 0.205800000 0.500000000 I -0.294200000 -0.207600000 0.500000000 C 0.544000000 0.921000000 0.784000000 H 0.609200000 1.002100000 0.769900000 H 0.557300000 0.845500000 0.724600000 H 0.551500000 0.875200000 0.864300000 N 0.389000000 0.987000000 0.767000000 H 0.324700000 0.913900000 0.730300000 H 0.381400000 1.068100000 0.734300000 H 0.339300000 0.990800000 0.831000000 K_POINTS automatic 1 1 1 0 0 0 Thank you all. 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: thc...@exeter.ac.uk<mailto:thc...@exeter.ac.uk> LinkedIn: https://uk.linkedin.com/in/edmundchan1 [uoe] [cid:image002.gif@01D2F1A2.9AF74CE0]
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