Dear Roberto, It seems to depend very much on the basis set you use. When I use the DZP basis set and corresponding pseudopotentials from the Siesta website (Sitm2distrib.Sidzp.basis and Ctm2lda.CDZPshort.basis), for 3C-SiC I get a charge transfer of 0.545 electrons from Si to C, as one would expect. On the other hand, with a DZP basis set created automatically by Siesta, I get a result similiar to yours, a charge transfer of 0.516 electrons from C to Si. Recently, there was an email that reported the same problem for a water molecule.
Yours, Wolfgang On Wednesday 20 July 2005 09:51, Roberto wrote: > Dear all: > > I have performed calculations for a silicon carbide (SiC) material. > Analysis of Mulliken population revealed a charge transfer from C to > Si of about 0.45|e| (well, I believe so). For instance: > > Species: C > Atom Qatom Qorb > 2s 2s 2py 2pz 2px 2py 2pz 2px > 2Pdxy 2Pdyz 2Pdz2 2Pdxz 2Pdx2-y2 > 1 3.582 0.092 0.797 0.217 0.160 0.660 0.619 0.665 0.319 > 0.007 0.015 0.011 0.009 0.010 > 3 3.582 0.092 0.797 0.660 0.160 0.217 0.319 0.665 0.619 > > ... > > Species: Si > Atom Qatom Qorb > 3s 3s 3py 3pz 3px 3py 3pz 3px > 3Pdxy 3Pdyz 3Pdz2 3Pdxz 3Pdx2-y2 > 2 4.420 0.769 0.411 0.582 0.450 0.561 0.269 0.386 0.139 > 0.116 0.261 0.206 0.144 0.125 > 4 4.420 0.769 0.411 0.561 0.450 0.582 0.139 0.386 0.269 > 0.116 0.144 0.206 0.261 0.125 > > But, of course, I was expecting a charge transfer from Si to C. What > may be wrong? > > []s, > > Roberto
