# Multireference X-ray emission and absorption spectroscopy calculations from Monte Carlo configuration interaction

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13 Citations (Scopus)

## Abstract

We adapt the method of Monte Carlo configuration interaction to calculate core-hole states, and use this for the computation of X-ray emission and absorption energies. We consider CO, $$\hbox {CH}_{4}$$CH4, $$\hbox {NH}_{3}$$NH3, $$\hbox {H}_{2}\hbox {O}$$H2O, HF, HCN, $$\hbox {CH}_{3}\hbox {OH}$$CH3OH, $$\hbox {CH}_{3}\hbox {F}$$CH3F, HCl and NO using a 6-311G** basis. We also look at carbon monoxide with a stretched geometry and discuss the dependence of its results on the cutoff used. The Monte Carlo configuration interaction results are compared with EOM-CCSD values for X-ray emission, and with experiment for X-ray absorption. Oscillator strengths are also computed, and we quantify the multireference nature of the wavefunctions to suggest when approaches based on a single reference would be expected to be successful or not.

Original language English Theoretical Chemistry Accounts 134 5 14 Apr 2015 https://doi.org/10.1007/s00214-015-1656-0 Published - May 2015

## Keywords

• Monte Carlo configuration interaction
• X-ray absorption
• X-ray emission

## ASJC Scopus subject areas

• Physical and Theoretical Chemistry