A Simple Model For Scalar Relativistic Corrections To Molecular Total Atomization Energies

TL;DR

This paper presents a simple additive model that accurately predicts scalar relativistic corrections to molecular atomization energies using atomic electron populations, offering a quick and interpretable estimate without complex calculations.

Contribution

The authors introduce a linear additive model based on atomic s and p populations to estimate scalar relativistic corrections, simplifying and speeding up the analysis of reaction energies.

Findings

Model accounts for over 98% of variance in corrections for 200 molecules.

Adding p population changes improves accuracy, halving remaining error.

Model provides a zero-cost, a priori estimate for relativistic effects on reaction energies.

Abstract

Scalar relativistic corrections to atomization energies of 1st-and 2nd-row molecules can be rationalized in terms of a simple additive model, linear in changes in atomic s populations. In a sample of 200 first-and second-row molecules, such a model can account for over 98% of the variance (99% for the first-row subset). The remaining error can be halved again by adding a term involving the change in atomic p populations: those coefficients need not be fitted but can be fixed from atomic electron affinity calculations. This model allows a fairly accurate a priori estimate for the importance of scalar relativistic corrections on a reaction energy, at essentially zero computational cost. While this is not a substitute for explicit calculation of Douglas-Kroll-Hess (DKH) or exact two-component (X2C) relativistic corrections, the model offers an interpretative tool for the chemical analysis of scalar relativistic contributions to reaction energies.