Static field-gradient polarizabilities of small atoms and molecules in finite temperature

TL;DR

This paper introduces new estimators for static field-gradient polarizabilities at finite temperatures using PIMC simulations, providing both ground state and non-adiabatic data for small atoms and molecules, highlighting thermal effects and rovibrational influences.

Contribution

The work presents novel, simple estimators for field-gradient polarizabilities in finite temperature PIMC, including non-adiabatic results, which are important for accurate modeling of thermal and rovibrational effects.

Findings

Good agreement with literature for ground state properties

Non-adiabatic polarizability data from 50 K to 1600 K

Identification of thermal and rovibrational effects in polarizabilities

Abstract

In this work, we propose new field-free estimators for static field-gradient polarizabilities in finite temperature PIMC simulation. Namely, dipole--quadrupole polarizability $A$, dipole--dipole--quadrupole polarizability $B$ and quadrupole--quadrupole polarizability $C$ are computed for several up to two-electron systems: H, H$^-$, He, Li$^+$, Be$^{2+}$, Ps$_2$, PsH, H$_2^+$, H$_2$, H$_3^+$ and HeH$^+$. We provide complementary data for ground state electronic properties within the adiabatic approximation, and demonstrate good agreement with available values in the literature. More importantly, we present fully non-adiabatic results from 50 K to 1600 K, which allow us to analyze and discuss strong thermal coupling and rovibrational effects in total field-gradient polarizabilities. These phenomena are most relevant but clearly overlooked, e.g., in the construction of modern polarizable force field models. However, our main purpose is demonstrating the accuracy and simplicity of our approach in a problem that is generally challenging.