# A new generation of effective core potentials from correlated calculations: 4s and 4p main group elements and first row additions

## TL;DR

This paper introduces a new method for generating effective core potentials (ECPs) using correlated calculations, resulting in more accurate and consistent pseudopotentials for main group elements, including relativistic effects.

## Contribution

The authors develop a novel correlation consistent ECP generation method applied to 3rd-row main group elements, improving accuracy and transferability over existing pseudopotentials.

## Key findings

- ccECPs reproduce AE spectra more accurately than existing pseudopotentials.
- ccECPs show better consistency across multiple properties.
- Transferability tests on molecules demonstrate reliable performance.

## Abstract

Recently, we developed a new method for generating effective core potentials (ECPs) using valence energy isospectrality with explicitly correlated all-electron (AE) excitations and norm-conservation criteria. We apply this methodology to the 3$^{rd}$-row main group elements, creating new correlation consistent effective core potentials (ccECPs) and also derive additional ECPs to complete the ccECP table for H-Kr. For K and Ca, we develop Ne-core ECPs and for the $4p$ main group elements, we construct [Ar]$3d^{10}$-core potentials. Scalar relativistic effects are included in their construction. Our ccECPs reproduce AE spectra with significantly better accuracy than many existing pseudopotentials and show better overall consistency across multiple properties. The transferability of ccECPs is tested on monohydride and monoxide molecules over a range of molecular geometries. For the constructed ccECPs we also provide optimized DZ - 6Z valence Gaussian basis sets.