On the basis-set extrapolation

TL;DR

The paper discusses basis-set extrapolation in quantum chemistry, revealing that the exponents used vary across the system, impacting the accuracy of potential energy surfaces and proposing ways to address this variability.

Contribution

It introduces the variability of extrapolation exponents across different system positions and explores methods to improve PES accuracy.

Findings

Exponents α and β are not constant but vary spatially.

Variable exponents affect the accuracy of potential energy surfaces.

Strategies to handle exponent variability are discussed.

Abstract

A possible solution for the problem of memory-size and computer-time, is the extrapolation of basis-set$^1$. This extrapolation has two exponents $\alpha$ and $\beta$, corresponding to the HF (reference energy) and the energy of correlations (EC), respectively. For a given system, the exponents are taken as constant$^2$, and potential energy surfaces (PES) are generated. We have found that the values of $\alpha$ and $\beta$ are not constant, but vary from position to position in the system. How to deal with such situation and get very accurate PES, is discussed.