Hello and hi all,
Within DFT+U calculation, what is the effect of parameter U on the band structure of a material in the non-spin polarized calculation (or paramagnetic phase. It is assumed that the material can be both PM and FM)?
Any suggestion or comment will be greatly appreciated.
Hi Quang Tran Van,
The U parameter removes the self-interaction error of standard DFT calculations. Typically the band-gap in standard DFT is underestimated, especially for transition metal bearing insulators, and small band gap insulators may be predicted as metallic. DFT + U mitigates this failure by removing the self-interaction error, and therefore widening the band-gap. Very good results may be obtained by calculating the value of U from first principles, preferably in a self consistent manner (see this paper Article Self-consistent Hubbard parameters from density-functional p...
), which can be done using the hp.x code of Quantum ESPRESSO. Here are some tutorials on how to do this (https://gitlab.com/QEF/q-e/tree/0c54e893feb35de42695d2d231495d8604224045/HP/examples). Also very good explanations of DFT + U are given in these videos (https://www.youtube.com/watch?v=nRaGp7purBs&t=7274s&ab_channel=MaterialsCloud from 1:58:50) and https://www.youtube.com/watch?v=WSABAqPWNH0&t=280s&ab_channel=QuantumESPRESSOHTH,
Johannes
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