Toward Systematic Quantum Embedding of Electrons and Charged Harmonic Oscillators

Many phenomena in physics, chemistry, and biology (solvents, membranes, nano-inclusions) can be described by embedding explicit molecules into an implicit environment. The coupling between both subsystems is typically treated via an approximate electrostatic or polarizable model [1]. Here, we aim at a systematic quantum treatment of molecular and environmental degrees of freedom modelled by a system of merged nuclei/electrons and charged quantum harmonic oscillators (QHOs). For this purpose, we construct a general Hamiltonian describing an embedded electronic domain in an environment of QHOs and present a variational ansatz, describing the full correlated ground state, integrated and optimized through quantum Monte Carlo methods [2]. Since charged QHOs, obtained by mapping many-body interactions onto a single quantum particle, are able to successfully reproduce the long-range response of real matter [3] with a reduced number of degrees of freedom, our new approach opens to the possibility of describing large systems at the full quantum level, yet at a low computational cost, uncovering important quantum effects between the electronic domain and the environment.

[1] Chemical Reviews 115, 5678 (2015)
[2] Chemical Reviews 112, 263 (2012)
[3] Chemical Reviews 117, 4714 (2017)