<table cellspacing="0" cellpadding="0" border="0" ><tr><td valign="top" style="font: inherit;">Dear All<br><br>I am plotting density of states for unrelaxed and
relaxed calculations of cubic SiC with B, Al and Ga as substitutional
impurity. Substitutions are done for both Si and C sites separately. The
density plot without relaxation looks OK. But after relaxation the
density plot undergoes a drastic change. I am not able to understand
whats going wrong. Here I am sending the density plots for all the cases
with and without relaxation. In all the figures the top of valence band
is taken as zero on the energy axis. Calculations are done with a
supercell of 128 atoms with one single impurity atom in it. The dashed
(purple) line is the Fermi energy. The dotted line shows the calculated
band gap. I am aslo giving here a portion of the relaxed input file
used for calculations.<br><br> &control<br>
calculation='relax'<br> restart_mode='from_scratch',<br>
prefix='sic',<br> pseudo_dir = '/espresso-4.0.5/pseudo/',<br>
outdir='/tmp/'<br> tprnfor= .TRUE.<br> /<br> &system<br>
ibrav=2, celldm(1) =32.9648, nat=128, ntyp=3,<br> nspin = 2,<br>
starting_magnetization(1)=0.0,starting_magnetization(2)=0.0,<br>
starting_magnetization(3)=0.0,<br> ecutwfc = 30.0,<br>
occupations='smearing', smearing='methfessel-paxton', degauss=0.02<br> /<br> &electrons<br>
mixing_beta = 0.7<br> /<br>&IONS<br> pot_extrapolation =
"second_order",<br> wfc_extrapolation = "second_order",<br> /<br>ATOMIC_SPECIES<br>
Si 28.086 Si.pz-vbc.UPF<br> C
12.00 C.pz-vbc.UPF<br> Al 26.98154 Al.pz-vbc.UPF<br><br>As ssen
in figure after relaxation we found mane levels inside band gap at there
is no gap for Al and Ga case. How is this possible? I have also done
for few other impurities and in most of the cases the C site
substitution after relaxation gives multiple levels inside band gap. Can
anybody please clarify whats going wrong?<br><br>Thanks in advance.<br>regards<br><br>Padmaja Patnaik<br>
Research Scholar<br>
Dept of Physics<br>
IIT Bombay<br>
Mumbai, India</td></tr></table>