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In the following exercise we are going to investigate the effect of defects in bulk silicon (mainly on the energy).
Use the input file as given below:
&GLOBAL PROJECT silicon8 RUN_TYPE ENERGY PRINT_LEVEL MEDIUM &END GLOBAL &FORCE_EVAL METHOD Quickstep STRESS_TENSOR ANALYTICAL &DFT BASIS_SET_FILE_NAME BASIS_SET POTENTIAL_FILE_NAME POTENTIAL &POISSON PERIODIC XYZ &END POISSON &SCF SCF_GUESS ATOMIC EPS_SCF 1.0E-8 MAX_SCF 500 &END SCF &XC &XC_FUNCTIONAL PBE &END XC_FUNCTIONAL &END XC &END DFT &SUBSYS &KIND Si ELEMENT Si BASIS_SET DZVP-GTH-PBE POTENTIAL GTH-PBE &END KIND &CELL ABC 5.430697500 5.430697500 5.430697500 PERIODIC XYZ &END CELL &COORD SCALED Si 0 0 0 Si 0 2/4 2/4 Si 2/4 2/4 0 Si 2/4 0 2/4 Si 3/4 1/4 3/4 Si 1/4 1/4 1/4 Si 1/4 3/4 3/4 Si 3/4 3/4 1/4 &END COORD &END SUBSYS &END FORCE_EVAL
Create a second input file
silicon64.inp based on the above with 64 atoms in the cell (do not use
MULTIPLE_UNIT_CELL but actually replicate the
Si … entries by hand and make sure you don't forget to update the
Run the calculation for both geometries and compare the single atom energy for both of them to make sure you got it right.
mpirun -np 4 cp2k.popt -i silicon64.inp -o silicon64.out
For both geometries create a vacancy by removing one Silicon, re-calculate the total energy and compare it to the total energy of the intact bulk Silicon minus the single atom energy. What do you observe? Why?
Finally, calculate the band structure for the silicon8 geometries (with and without vacancy) as shown in the exercise Projected density of states and Band structure for WO$_3$ between $\Gamma$, $X$, $K$, $\Gamma$ and compare them.
8 Bulk Silicon Si 0 0 0 Si 0 2.7153487500 2.7153487500 Si 2.7153487500 2.7153487500 0 Si 2.7153487500 0 2.7153487500 Si 4.07302312500 1.35767437500 4.07302312500 Si 1.35767437500 1.35767437500 1.35767437500 Si 1.35767437500 4.07302312500 4.07302312500 Si 4.07302312500 4.07302312500 1.35767437500