Introduction

PSIXAS is a plugin for the open-source quantum chemistry program Psi4 with the focus on the simulation of X-ray absorption phenomena, like X-ray photoelectron spectroscopy (XPS) and Near edge X-ray absorption fine structure spectroscopy (NEXAFS).

In addition to simulations that occur from the electronic ground state, it is also possible to simulate X-ray absorptions after a UV/Vis absorption, which is needed to model pump-probe or transient X-ray absorption experiments.

The plugin and the underlying theory are described in two publications [1 , 2]