# Second Virial Coefficients for N2···H2 and NH···NH

## TL;DR

This paper calculates thermodynamic properties of gas mixtures using intermolecular potentials, focusing on nitrogen and ammonia interactions.

## Contribution

A first-order correction to the ideal gas law is introduced using second virial coefficients derived from a many-body expansion potential.

## Key findings

- Second virial coefficients for H2···N2 agree with previous literature data.
- Computed values for NH···NH follow expected trends for similar systems.
- Thermodynamic properties were calculated for temperatures between 30–2000 K.

## Abstract

Thermodynamic properties of real gases can be accurately
described
using realistic intermolecular potential energy surfaces. In this
work, a first-order correction to the ideal gas equation of state
is introduced through the computation of the classical second virial
coefficient, B(T), derived from
the configurational partition function, which explicitly depends on
the intermolecular interaction potential. As a case study, the double
many-body expansion (DMBE) potential energy surface for the ground
electronic state of the N2H2 system was employed
to derive pairwise interaction potentials for H2···N2 and NH···NH. These potentials were used to
numerically evaluate the canonical partition function. Second virial
coefficients, compressibility factors, and constant-volume heat capacities
were computed in the temperature range 30–2000 K. The calculated B(T) values for H2···N2 are in good agreement with previous literature data, while
the results for NH···NH lie within expected trends
observed for similar systems.