Abstract

Wavefunction quantum chemistry methods such as coupled cluster theory are now being applied to solid systems [1]. While more expensive in computational cost, they promise to give ab initio properties with a more obvious systematic improvable accuracy than density functional theory (DFT). Metals prove challenging for wavefunction methods due to the vanishing gap. We studied the bulk modulus, lattice parameter and cohesive energy of lithium and aluminium with coupled cluster singles and doubles (CCSD) [2]. To reduce the CCSD error, a coarse grained version of perturbative triples was tested as well as scaling the energy using information from the CCSD error in the uniform electron gas [3].

References:

[1] See e.g. Bartlett and Musiał, RMP 79 , 291 (2007), Hirata et al., JCP 120 , 6 (2004), Booth et al., Nature 493, 7432 (2013), McClain et al., JCTC , 13, 3 (2017).

[2] Neufeld, Ye and Berkelbach, arXiv:2204.01563.

[3] Shepherd, JCP 145 , 031104 (2016), Ceperley and Alder, PRL 45 , 566 (1980).