Dear users, I'm trying to perform a convergence test for CaSiO3 tetragonal phase. Following is my input : #!/bin/sh
for aa in 5.6131 do for cc in 7.181 7.182 7.183 7.184 7.185 do for k in 8 do for ecut in 30 do cat > ${aa}_${cc}_${k}_${ecut}.in << EOF &control calculation = 'scf', prefix = '${aa}_${cc}_${k}_${ecut}' tprnfor=.true. tstress=.true. outdir = '/home/user/PNV/CaSiO3_tetragonal/' pseudo_dir = '/home/user/PNV/CaSiO3_tetragonal/pseudo/' / &system ibrav = 7, A=$aa C=$cc nat = 10, ntyp = 3, ecutwfc = $ecut, / &electrons diagonalization='david' mixing_mode = 'plain' mixing_beta = 0.7 conv_thr = 1.0d-12 / ATOMIC_SPECIES Ca 40.078 Ca.pz-spn-kjpaw_psl.1.0.0.UPF Si 28.0855 Si.pz-n-kjpaw_psl.0.1.UPF O 15.999 O.pz-n-kjpaw_psl.0.1.UPF ATOMIC_POSITIONS {crystal} Ca 0.250 0.750 0.500 Ca 0.750 0.250 0.500 Si 0.000 0.000 0.000 Si 0.500 0.500 0.000 O 0.222 0.722 0.9441 O 0.250 0.250 0.000 O 0.278 0.222 0.500 O 0.722 0.778 0.500 O 0.750 0.750 0.000 O 0.778 0.278 0.0559 K_POINTS (automatic) $k $k $k 1 1 1 EOF mpirun -np 40 -machinefile x2 /apps/codes/qe/6.5/bin/pw.x < ${aa}_${cc}_${k}_${ecut}.in > ${aa}_${cc}_${k}_${ecut}scf.out done done done done To perform the test, I fixed c=7.182 angstrom and varied 'a'. The value of 'a' for which I attained zero pressure was 5.6131 angstrom, which is quite different from other theoretical finding which is a=4.9812 angstrom ( https://sci-hub.se/https://doi.org/10.1107/s0108768106035762). The error in 'a' is about 10-12%, which is quite large. Can I know why I am getting this much discrepancy in lattice constant? And how can I get the correct value of 'a'?
_______________________________________________ Quantum ESPRESSO is supported by MaX (www.max-centre.eu) users mailing list users@lists.quantum-espresso.org https://lists.quantum-espresso.org/mailman/listinfo/users