<span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">We simulate a tantalate system using LDA+U. We use small k-points, 18, k-points, and SCF is done in less than 20 cycles. Then it is followed by LDA+U. After LDA+U, we do DOS and bandstrtucture calculation separately.</span><br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">
<br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px"><span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">DOS calculation is straight forward in Wien2k. For our system, the space group is 13, and thus we refer to </span><a href="https://mail2.usm.my/owa/redir.aspx?C=6b51c784aa744c6aa0f9b75ad7f9c13e&URL=http%3a%2f%2fwww.cryst.ehu.es%2fcryst%2fget_kvec.html" target="_blank" style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">http://www.cryst.ehu.es/cryst/get_kvec.html</a><span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px"> to generate k-mesh, since we need to plot (Gamma, Z, Y, A, B, D, E) points and we believe that the default and available simple_cubic, bcc, hcp and fcc cannot generate the case.klist_band file we want. </span><br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">
<br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px"><span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">The problem now is the band-gap value from DOS and bandstrcuture calculation are the same if we do not do any "Gauss-broadening"(G-b) in the DOS. It means, if we stick to the default G-b of 0.003, band-gaps from DOS and Bandstrcuture calculation are basically the same. But if we change the G-b from 0.003 to, say 0.008, the band gap is observed to change to smaller value, >10% less than the value before. </span><br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">
<br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px"><span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">Can someone give the reasoning why there is such a difference occured? By the way, the reason why we adjust the value for G-b is because the graph will look more resemblance to experimental data plot rather than "spiky" features for smaller value of G-b</span><br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">
<br style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px"><span style="font-family:Tahoma,'Sans Serif',Arial;font-size:15px">and how to read the values for band-gap? do we read from DOS plot or bandstructure plot?</span>