Towards quantum-chemical method development for arbitrary basis functions

TL;DR

This paper introduces molsturm, a flexible, open-source quantum-chemical framework supporting arbitrary basis functions, enabling rapid development and testing of new electronic structure methods.

Contribution

The paper presents a basis-function-independent self-consistent field scheme implemented in molsturm, facilitating method development and comparison across different basis function types.

Findings

Implemented coupled-cluster doubles with arbitrary basis functions

Demonstrated gradient-free geometry optimization using molsturm

Showcased flexible integration with third-party packages

Abstract

We present the design of a flexible quantum-chemical method development framework, which supports employing any type of basis function. This design has been implemented in the light-weight program package molsturm, yielding a basis-function-independent self-consistent field scheme. Versatile interfaces, making use of open standards like python, mediate the integration of molsturm with existing third-party packages. In this way both rapid extension of the present set of methods for electronic structure calculations as well as adding new basis function types can be readily achieved. This makes molsturm well-suitable for testing novel approaches for discretising the electronic wave function and allows comparing them to existing methods using the same software stack. This is illustrated by two examples, an implementation of coupled-cluster doubles as well as a gradient-free geometry optimisation, where in both cases, an arbitrary basis functions could be used. molsturm is open-source and can be obtained from https://molsturm.org.