Development of a practical multicomponent density functional for electron-proton correlation to produce accurate proton densities

Abstract

Multicomponent density functional theory (DFT) enables the consistent quantum mechanical treatment of both electrons and protons. A major challenge has been the design of electron-proton correlation functionals that produce even qualitatively accurate proton densities. Herein an electron-proton correlation functional, epc17, is derived analogously to the Colle-Salvetti formalism for electron correlation and is implemented within the nuclear-electronic orbital (NEO) framework. The NEO-DFT/epc17 method produces accurate proton densities efficiently and is promising for diverse applications.

How intrinsic nuclear nonadiabaticity affects molecular structure, electronic density, and conformational stability: Insights from the multicomponent DFT calculations of Mu/H isotopologues

“…This facilitates the unambiguous assignment of well‐documented experimental data based on the successful history of DFT methods in this field . Admittedly, the recent development of electron‐proton correlation functionals seems to shed light on the conceivable approach for extending any electron‐muon correlation functional in future, although the detailed examination of their implications remains to be done even in the case of proton . Notwithstanding, the development of the electron‐muon correlation functionals is expected to be more challenging taking account of muon's high susceptibility to nonadiabatic behavior due to its considerably lower mass relative to that of the proton.…”

“…This task has been extensively addressed in the form of multicomponent extensions of the configuration interaction , perturbation theory , coupled cluster formalism , and density functional theory (DFT) . The latter is indeed most intriguing due to its capabilities of being computationally “practical” and providing experimentally accurate results as revealed by the recent developments of the proton‐specific functionals . Thus, one of the theoretical objectives of the present account is based on this premise and we will, in fact, extend its applicability scope and concomitantly benchmark its potential of computational scalability.…”

“…On the contrary, the development of an efficient electron‐muon correlation functional seems elusive and is yet to be deduced. Nonetheless, based on the recent attempts to devise electron‐nucleus functionals , the efforts to find a general‐purpose functional for a particular nucleus may not be accessible and property‐specific functionals should be seen as an attainable goal. Presumably, the electronic exchange‐correlation contribution is the predominant part of total correlation energy and, therefore, its incorporation would considerably improve the quality of one‐electron density.…”

The any particle molecular orbital approach: A short review of the theory and applications

“…LDA functionals have been proposed to include the proton–electron and positron‐electron correlation effects in the self‐consistent field (SCF) cycle. We are evaluating the range of applicability of these functionals in molecular systems.…”

“…The MC‐DFT approach can be utilized to study NQEs. In these calculations, the exchange‐correlation functional comprises three contributions: the electronic exchange‐correlation functional, , which is usually borrowed from electronic structure DFT; the nuclear exchange‐correlation, , which is neglected since it has been found to be negligible and the nuclear‐electron correlation, , for which local density approximation (LDA) functionals have been proposed . Still, in some applications of APMO‐DFT, the nuclear‐electronic correlation has been neglected …”