# Quantum states of confined hydrogen plasma species: Monte Carlo calculations

## TL;DR

This paper employs a symmetry-based diffusion Monte Carlo method to calculate quantum energy states of confined hydrogen ions, providing a versatile approach for studying hydrogen plasma species in solid environments.

## Contribution

It introduces a simple, effective Monte Carlo technique for calculating quantum states of confined hydrogen ions applicable to various cavity shapes and plasma species.

## Key findings

- Accurate energy states for H2+ under spherical confinement.
- Method applicable to cavities of arbitrary shape.
- Potential for studying hydrogen species in crystal environments.

## Abstract

The diffusion Monte Carlo method with symmetry-based state selection is used to calculate the quantum energy states of H$_2^+$ confined into potential barriers of atomic dimensions (a model for these ions in solids). Special solutions are employed permitting one to obtain satisfactory results with rather simple native code. As a test case, $^2\Pi_u$ and $^2\Pi_g$ states of H$_2^+$ ions under spherical confinement are considered. The results are interpreted using the correlation of H$_2^+$ states to atomic orbitals of H atoms lying on the confining surface and perturbation calculations. The method is straightforwardly applied to cavities of any shape and different hydrogen plasma species (at least one-electron ones, including H) for future studies with real crystal symmetries.