Unharmonic adiabatic potential by short-range correlation effect enlarging C₃₃ of crystalline graphite

In our previous work using the LDA+U+RPA method [1], we reported a theoretical value of C₃₃ of graphite as large as 48GPa when cRPA estimation of the on-site U for 2p-orbitals is used. Renormalization in Wannier functions determined at each point on the adiabatic potential surface is essential. Fixed localized orbital cannot cause the enhancement of C₃₃ from a value by ACFDT-RPA, which is more than 20% smaller than the observed C₃₃ of defect-free monocrystalline graphite. In this presentation, after discussing relevance of the multi-reference extension of DFT[2] for beyond-RPA approaches, we open comparison among several +U approaches with the double-counting term.
[1] K. Kusakabe, A. Wake, A. Nagakubo, K. Murashima, M. Murakami, K. Adachi, H. Ogi, Phys. Rev. Mater. 4, 043603 (2020). [2] K. Kusakabe, J. Phys. Soc. Jpn. 70, 2038 (2001).