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<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Dear all,</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">I ran a band structure calculation for the planar graphene-like SiC.</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Using the following input, I got a direct gap of 2.16 eV at K symmetry point.</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Now there is a question for me.</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">The literature generally report a direct gap of ~2.55 eV at K symmetry point.</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">I also tried ELK code (based on FP-LAPW method) and CASTEP code (based on norm conserving PBE pseudopotentials)</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">and, as expected, got a direct gap of ~2.55 eV at K symmetry point.</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Note that, the following input is only for quick test.</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">I have calculated the whole band structure along the G-K-M-G path
with 150 k-points, </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">and gotten a direct gap of 2.16 eV at K symmetry point.</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">I have changed some parameters such as 'ecutwfc' and *.UPF, and no change was observed.</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Any suggestions?</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Best regards</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Youzhao Lan</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">***************************</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">&control</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> calculation='scf'</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> prefix='SiC111'</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> /</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">&system</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">ibrav=0,nat=2,ntyp=2</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">ecutwfc = 80.0</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">nbnd=8</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> /</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> &electrons</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> /</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">ATOMIC_SPECIES</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">Si 28.06 Si.pbe-mt_fhi.UPF</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">C 12.01 C.pbe-mt_fhi.UPF</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">CELL_PARAMETERS (bohr)</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 5.07289346 -2.92883646 0.00000000 </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 0.00000000 5.85767273 0.00000000 </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 0.00000000 0.00000000 37.80921171 </DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">ATOMIC_POSITIONS (crystal)</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> C 0.000000 0.000000 0.500000</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> Si 0.333333 -0.333333 0.500000</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">K_POINTS (crystal)</DIV>
<DIV style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 3</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 0.000 0.000 0.000 1.0</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 0.333 0.333 0.000 1.0</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> 0.500 0.000 0.000 1.0</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman">**************************************</DIV>
<DIV
style="FONT-SIZE: 12pt; FONT-FAMILY: Times New Roman"> </DIV></DIV></BODY></HTML>