Hi there, I'm using QE 6.5 to run a relaxation simulation with FeSi(NaCl structure) supercell. I put 8 atoms in the cell and I used simple cubic for crystal symmetry. Here's the input script I used:
&control calculation='vc-relax', prefix='FeSi_vc-relax_fixed' pseudo_dir='/home/kchen/PSEUDO/' / &system ibrav=1, celldm(1)=9.032891, nat=8,ntyp=2, ecutwfc=100, ecutrho=1500, occupations='fixed' / &electrons mixing_beta=0.3, electron_maxstep=300 / &ions / &cell cell_dynamics='bfgs' / ATOMIC_SPECIES Fe 55.845 Fe.pbe-spn-rrkjus_psl.1.0.0.UPF Si 28.0855 Si.pbe-n-rrkjus_psl.1.0.0.UPF ATOMIC_POSITIONS (crystal) Fe 0 0 0 Si 0.5 0 0 Fe 0.5 0.5 0 Si 0 0.5 0 Fe 0.5 0 0.5 Si 0 0 0.5 Fe 0 0.5 0.5 Si 0.5 0.5 0.5 K_POINTS (automatic) 6 6 6 1 1 1 I got the final Fe-Si bond length as 2.33 A and Heat of Formation as 0.04eV/atom. However, in the reference, https://journals.aps.org/prb/pdf/10.1103/PhysRevB.85.245102, page 6, Table VI, the bond length is around 2.37A, which is close to my result but the heat of formation is 0.25 eV/atom. I don't know what I'm doing wrong. For potential energy of Fe and Si. I used 1 Fe atom in bcc crystal and 2 Si atoms in fcc crystal for their potential energies. You can find the script I used in the attachment. The potential energy for bcc Fe and dia Si I got are -247.789Ry/atom and -11.4201Ry/atom respectively. I also tried SCF calculation with the bond length provided in the reference, but it did not help a lot. Thank you for your help Kefan Ph.D. student Department of Chemical and Materials Engineering University of Nevada, Reno, USA
Si2_dia.in
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Fe_bcc.in
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