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<DIV><FONT face=Arial size=2>Hello,</FONT></DIV>
<DIV><FONT face=Arial size=2>I have written about this problem before but am
still stuck. So please help oncemore.</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>I optimised hematite (Fe2O3) which has the
same space group as Al2O3 (167 R-3c). I used the structure file in "Examples" of
Wien and the experimental values of cell parameters (a=b=5.035 Ang, c= 13.747
Ang, angles, 90). The optimised volume is around -10 to -12%, whatever the
exchange functional I use (13, 5, 14). I did both c/a and vol
optimisation for all these. I also did this with spin-orbit coupling. The
volumes come very far from experimental. Band gap is also too small (~ 0.3eV).
(I used 600 k points, RMT= 1.8 for Fe and 1.6 for O).</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2>My question is :</FONT></DIV>
<DIV><FONT face=Arial size=2>(i) Will Wien not work for a strongly
correlated system like Fe2O3? </FONT></DIV>
<DIV><FONT face=Arial size=2>(ii) Can I change the inst file to reflect the
actual oxidation state of Fe (3+) and O (2-). In this case Fe would have
only 5 outer electrons (Ar, 3d5) and O would have He, 2s2,
2p6.</FONT></DIV>
<DIV><FONT face=Arial size=2>Is it permitted to change the inst file and
transfer 3 electrons from Fe to O? This may be a silly question but I do not
know.</FONT></DIV>
<DIV><FONT face=Arial size=2>Thank you for your time,</FONT></DIV>
<DIV><FONT face=Arial size=2>Chandrika</FONT></DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial size=2></FONT> </DIV>
<DIV><FONT face=Arial
size=2>-----------------------------------------------------------------------------------</FONT></DIV>
<DIV><FONT face=Arial size=1>Dr (Ms) Chandrika Varadachari<BR>Raman Centre for
Applied and Interdisciplinary Sciences<BR>16 A Jheel Road<BR>Calcutta
700075<BR>India</FONT></DIV>
<DIV><FONT size=1></FONT> </DIV>
<DIV><FONT face=Arial size=1>Tel : 91-33-24830029<BR>Fax
91-33-24180610<BR></FONT></DIV></BODY></HTML>