# Cage occupancies in nitrogen clathrate hydrates from Monte Carlo simulations

## TL;DR

This study uses Monte Carlo simulations to compare with experimental data on nitrogen hydrate cage occupancies, aiming to improve potential models and interpret occupancy ratios at specific conditions.

## Contribution

The paper introduces a new N-O interaction potential derived from ab-initio data, enhancing the accuracy of simulations for nitrogen hydrate cage occupancies.

## Key findings

- Simulations with the new potential match experimental occupancy ratios more accurately.
- Some existing potentials fail to reproduce double occupancy in large cages.
- Refined potentials help interpret high cage occupancy ratios at 273 K and high pressures.

## Abstract

Comparisons of Gibbs ensemble Monte Carlo simulations with experimental data for the cage occupancies in N2 clathrate hydrates are performed to assess the accuracy of such simulations, to refine the effective potentials employed, and to help interpret recently measured large cage over small cage occupancy ratios [Petuya et al., J. Phys. Chem. C 122, 566 (2018)]. Different sets of interaction potentials for N2-N2, N2-H2O and H2O-H2O interactions are considered. Some of them fail to reproduce the known experimental fact that some large cages are doubly occupied at 273 K and high pressures. The best agreement between simulations and experiments is obtained when using a new N-O interaction potential derived in this work by averaging an ab-initio potential energy surface for the N2-H2O dimer.