# Singling Out Dynamic and Nondynamic Correlation

## TL;DR

This paper analyzes the correlation components of pair density to distinguish between dynamic and nondynamic correlation, revealing key factors for describing dispersion forces and guiding the development of advanced electronic structure methods.

## Contribution

It introduces a method to classify molecular systems based on correlation components and identifies the key factors influencing dispersion forces and correlation types.

## Key findings

- Correlation parts of pair density can be separated into short-range and long-range components.
- Long-range asymptotics reveal the universal decay related to London dispersion forces.
- Identification of correlation types aids in developing new electronic structure methods.

## Abstract

The correlation part of the pair density is separated into two components, one of them being predominant at short electronic ranges and the other at long ranges. The analysis of the intracular part of these components permits to classify molecular systems according to the prevailing correlation: dynamic or nondynamic. The study of the long-range asymptotics reveals the key component of the pair density that is responsible for the description of London dispersion forces and a universal decay with the interelectronic distance. The natural range-separation, the identification of the dispersion forces, and the kind of predominant correlation type that arise from this analysis are expected to be important assets in the development of new electronic structure methods in wave function, density, and reduced density-matrix functional theories.