Experimentally constrained wave function method

TL;DR

This paper extends quantum crystallography methods to incorporate multiple experimental observables, including excited states, enabling more comprehensive wavefunction reconstructions using advanced electronic structure techniques.

Contribution

It introduces a theoretical framework that integrates various experimental data into wavefunction fitting, expanding beyond traditional x-ray diffraction constraints.

Findings

Framework allows inclusion of optical and spectroscopic data

Implementation details for Hartree-Fock and Coupled Cluster methods

Enables simultaneous fitting of multiple experimental observables

Abstract

In this work, we extend the x-ray constrained wavefunction fitting approach, a key method in quantum crystallography for charge density reconstruction, to incorporate experimental observables beyond x-ray diffraction. Unlike traditional quantum crystallography methods, which are typically limited to molecules in their ground states, our approach integrates excited states. This advancement will enable simultaneous fitting of x-ray diffraction data alongside optical and x-ray spectroscopic data. We introduce a comprehensive theoretical framework that allows for the inclusion of any experimental observable as a constraint in wavefunction reconstruction. Furthermore, we provide detailed derivations and instructions for implementation of this method using two electronicstructure methods: a generalized Hartree-Fock method for excited states and the Coupled Cluster Equation-of-motion method.