GAMMA
The GAMMA file is an input file used with the ICHARG=5 tag. It's employed during electronic minimization to add occupations per k-point and orbital before calculating a new charge density. The file's format is structured as follows:
567 -1 ! Number of k-points, default number of bands 1 81 92 -0.88697620213424 -0.00000000000110 0.00952263319978 -0.00013538025816 -0.00003023919061 0.00036153047962 … 0.00952263319978 0.00013538025816 -0.90621349117750 -0.00000000000092 -0.00002036611614 0.00020787085249 … … (10 more lines) 2 81 92 -0.89265621432703 -0.00000000000107 -0.00944765243065 -0.00671452451385 -0.00029309275635 -0.00012146585216 … (11 more lines) … 567 82 91 -0.89056253498876 -0.00000000000112 -0.00449699353373 0.00290102672201 -0.00014095045304 0.00000787119531 -0.00289794970644 …
The file contains a small header marking the number kpoints (must be consistent with the current number of kpoints in the irreducible Brillouin zone, and if there is a default number of bands it should assume for each kpoint. Then follows a line that increments the kpoint parsed and the band window, i.e. the indices of bands for which the occupation changes are read in. Next, comes a nband times nband matrix one row per line, where complex number formatting is used, first number is the real part and the second is the complex part etc.
While ICHARG=5 is set, Vasp will only run while the file vasp.lock is present in the current directory. Vasp will wait right before the GAMMA is read and check if such file is present. If not Vasp will wait for an external process to create it. This useful to write and interface to an external code that performs in each SCF step some extra computation and updates the KS occupations. The TRIQS software package[1] makes use of it to perform charge self-consistent DFT plus dynamical mean field theory (DMFT) calculations[2][3], and provides tutorials on how to perform such calculations with VASP[4][5].
Related tags and articles
References
- ↑ O. Parcollet, M. Ferrero, T. Ayral, H. Hafermann, I. Krivenko, L. Messio and P. Seth, Computer Physics Communications 196, 398 (2015).
- ↑ M. E. Merkel, A. Carta, S. Beck and Alexander Hampel, Journal of Open Source Software 7, 77 (2022).
- ↑ M. Aichhorn, L. Pourovskii, P. Seth, V. Vildosola, M. Zingl, O. E. Peil, X. Deng, J. Mravlje, G. J. Kraberger, C. Martins, M. Ferrero, O. Parcollet, Computer Physics Communications 204, 200 (2016).
- ↑ triqs.github.io/dft_tools/latest/tutorials.html#vasp-interface-examples (2024).
- ↑ triqs.github.io/solid_dmft/tutorials/PrNiO3_csc_vasp_plo_cthyb/tutorial (2024).