Thank you Yun-Peng, Computationally how i do this 12 atoms 8x8x8 = 432 atoms Gamma. I guess it should be. I'm not plotting DOS, i'm looking at the eigevalues spitted.
With Best Regards, Andrei Buin. On Tue, Aug 20, 2013 at 10:04 PM, Yun-Peng Wang <[email protected]>wrote: > Hi, > > My question is, is the R point of the 12 atoms unit cell equivalent to the > Gamma point of 432 atoms unit cell? > > The band gap should be estimated from density of states. Of course, > because of the finite number of k-points in practice and finite smearing, > the band gap estimated from density of states is usually not precise. The > most accurate method to determine the band gap is to plot the band > structure along symmetric paths. > > hope it helps > > Yun-Peng > > ------------------------------**-------------------------- > Yun-Peng Wang > Postdoctoral Associate > Department of Physics and the > Quantum Theory Project > University of Florida > [email protected] > > ------------------------------ > Date: Tue, 20 Aug 2013 21:50:02 -0400 > From: [email protected] > To: [email protected] > Subject: [SIESTA-L] Bizarre behaviour > > Dear Siesta users, > > I'm having very bizarre problem. > I'm simulating the primitive cubic unit cell(12 atoms) of the CH3N3SnI3 > perovksite with GGA and PBE and gives me band gap of Eg=0.9 eV at R point > with 8x8x8 Moshkrof automatic k sampling(i know it's wrong in DFT, but > still) and then i use supercell approach built in with 3x3x3 unit > cell(432 atoms) with Gamma point only and i get a bangap of 1.6 eV. I've > checked against plane cutoff convergence seems ok. I thought maybe > dispersion is too big so one should sample it more finely, but it turns > out meff=0.13me, which should be fine. Any ideas ? > > > With Best Regards, Andrei Buin. > >
