[Pw_forum] SCF_Calculation_Zeolite

[Mofrad, Amir Mehdi (MU-Student)]

Dear all,


I want to do an SCF calculation on sodalite (a kind of zeolite) unit cell (consisting 36 atoms) but I'm having some difficulties to do so. First off, I don't know what the vital and least parameters needed for these types of calculations are. So I used virtual nanolab to generate an input file. Following a tutorial on Quantum Wise website, I manipulated the input files, for instance they said to include nbnd=10, change the ecutwfc=30, etc.However, when I stared running the simulation, I kept getting an error "too few bands". So I started increasing the number by the order of 10 (without having any idea what it is!) and at nbnd=100 my simulations is now being run. I left other variables (such as K_POINTS) unchanged. I would really appreciate it if someone would tell me what should be and should not be in my input file for scf calculations and give me a sense of the range of numbers that I'm allowed to assign to the variables. Here is my input file:



&control

 calculation = 'scf'
 verbosity = 'high'
 restart_mode = 'from_scratch'
 prefix = 'SOD'
 tstress = .false.
 tprnfor = .false.
 pseudo_dir = './'
 outdir = '/tmp'
/

&system
 ibrav=0
 nat=36
 ntyp=2
 ecutwfc=30
 ecutrho=300
 nbnd=100
 input_dft='PBE'
/

&electrons
 diagonalization='david'
 mixing_mode = 'plain'
 mixing_beta = 0.7
 conv_thr =  1.0d-08
/

ATOMIC_SPECIES
 O 15.999400 O.pbe-kjpaw.UPF
 Si 28.085500 Si.pbe-rrkj.UPF


ATOMIC_POSITIONS bohr

 O 4.223852 10.209245 16.553687
 O 12.694549 1.738548 8.082990
 O 16.194639 10.209245 16.553687
 O 7.723942 1.738548 8.082990
 O 16.194639 10.209245 4.582900
 O 7.723942 1.738548 13.053597
 O 4.223852 10.209245 4.582900
 O 12.694549 1.738548 13.053597
 O 16.194639 4.223852 10.568293
 O 7.723942 12.694549 19.038991
 O 16.194639 16.194639 10.568293
 O 7.723942 7.723942 2.097596
 O 4.223852 16.194639 10.568293
 O 12.694549 7.723942 2.097596
 O 4.223852 4.223852 10.568293
 O 12.694549 12.694549 2.097596
 O 10.209245 16.194639 4.582900
 O 1.738548 7.723942 13.053597
 O 10.209245 16.194639 16.553687
 O 1.738548 7.723942 8.082990
 O 10.209245 4.223852 16.553687
 O 1.738548 12.694549 8.082990
 O 10.209245 4.223852 4.582900
 O 1.738548 12.694549 13.053597
 Si 5.973897 10.209245 19.038991
 Si 14.444594 1.738548 10.568293
 Si 14.444594 10.209245 2.097596
 Si 5.973897 1.738548 10.568293
 Si 1.738548 5.973897 10.568293
 Si 10.209245 14.444594 19.038991
 Si 1.738548 14.444594 10.568293
 Si 10.209245 5.973897 2.097596
 Si 10.209245 1.738548 6.332945
 Si 1.738548 10.209245 14.803642
 Si 10.209245 1.738548 14.803642
 Si 1.738548 10.209245 6.332945

K_POINTS gamma

CELL_PARAMETERS bohr
17.933187 0.000000 0.000000
0.000000 17.933187 0.000000
0.000000 0.000000 21.136587




Best regards,


Amir M. Mofrad

Graduate Research Assistant

Chemical Engineering Department

University of Missouri
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