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### Single-site DFT+DMFT for vanadium dioxide using bond-centered orbitals
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Peter Mlkvik, Maximilian E. Merkel, Nicola A. Spaldin and Claude Ederer
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#### Abstract:
We present a combined density-functional theory and single-site dynamical mean-field theory (DMFT) study of vanadium dioxide (VO2) using an unconventional set of bond-centered orbitals as the basis of the correlated subspace. VO2 is a prototypical material undergoing a metal-insulator transition (MIT), hosting both intriguing physical phenomena and the potential for industrial applications. With our choice of correlated subspace basis, we investigate the interplay of structural dimerization and electronic correlations in VO2 in a computationally cheaper way compared to other state-of-the-art methods such as cluster DMFT. Our approach allows us to treat the rutile and M1 monoclinic VO2 phases on an equal footing and to vary the dimerizing distortion continuously, exploring the energetics of the transition between the two phases. The choice of basis presented in this work hence offers a complementary view on the long-standing discussion of the MIT in VO2 and suggests possible future extensions to other similar materials hosting molecular-orbital-like states.
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All DFT calculations were performed using the Quantum Espresso code (v7.0) with the PBE exchange-correlation functional. All Wannier functions were produced using the Wannier90 code (v3.1.0). All DFT+DMFT calculations were done using solid_dmft utilizing TRIQS (v3.1.0) through the Docker file provided on solid_dmft github.

The main folder contains input files for all calculations presented in the paper, with subfolders indicating the type of calculation included. Each folder contains one or more "*.sh" scripts that run the calculation on the clusters used for the work.

Folder "1_bc_wfs" runs a DFT calculation combined with creation of bond-centered orbitals produced by the "bond_proj_amn.py" script. This can be done for both the "m1" and "rut" provided setups. An h5 archive used later is also produced.

Folder "2_crpa" performs a cRPA calculation using the RESPACK code communicating with a DFT calculation through the wan2respack package. This involves first a DFT calculation through "1_DFT.sh" and then a chiqw tensor calculation and W and J calculations through "2_start_chiqw.sh".

Folder "3_uj_scan" performs an array of one-shot DMFT calculations on top of the provided "*.h5" archive, which should be copied from "1_bc_wfs". The calculations are done for a set of differing U-J values.

Folder "4_dist_scan" performs a distortion scan from the R into the M1 VO2 phases. The directory "dummy_dist_test" includes the sample files that are then edited as outlined in "dist_scan.sh". A full charge-self consistent calculation is run for each distortion point. One needs to ensure that the bond_proj_amn.py is run at every step of the charge-self consistency loop.