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BSE calculation
Posted: Mon Nov 04, 2013 4:47 am
by flybird0303
[quote="'smallblacktext'>[ Edited Mon Nov 04 2013, 04:48AM "]</span>
BSE calculation
Posted: Tue Nov 05, 2013 4:03 am
by giacomo giorgi
Isabel. Please excuse me for the terribly late reply. I just noticed your post right now.
Flybird0303. In DFT you use an exchange-correlation potential (Vxc), in GW you use a screened Coulomb potential (W). This makes the difference
BSE calculation
Posted: Thu Nov 07, 2013 3:20 pm
by gbal
Hej people,
Thanks to this tread i was able to finish some BSE calculations. However, i went to get bibliografy for it and the methods seems to vary a bit (at least at first look). Do you know any references for the implementation in vasp? In the code they talk about Tamm-Dancoff approximation, but this ain't much help, as seems all the people use it.
Thanks a lot anyway!
BSE calculation
Posted: Wed Nov 27, 2013 2:31 pm
by yunhailiseu
[quote="yunhailiseu"]There are two basic electronic excitations : charged excitation in which one electron is removed from or added to the system, and neutral excitation in which the number of electrons remain unchanged. GW method is designed to deal with the former, while BSE for the later.
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[/quote]
Firstly, generate a large number of Kohn-Sham orbitals on a regular k-grid.
Secondly, do GW calculation using wavefunctions generated in DFT calculation to obtain quasi-particle energies.
Finally do BSE calculation.
GW gap describes the energy required to remove an electron from a N-electron system, while DFT gap is more like the energy required to excite an electron. It is obvious that removing an electron takes more energy.
<span class='smallblacktext'>[ Edited Wed Nov 27 2013, 02:34PM ]</span>