Quantum molecular dynamics simulations of the thermophysical properties of shocked liquid ammonia for pressures up to 1.3 TPa

TL;DR

This study uses quantum molecular dynamics to explore the thermophysical properties of shocked liquid ammonia at extremely high pressures and temperatures, revealing phase transitions and metallic states relevant to planetary interiors.

Contribution

First systematic quantum molecular dynamics simulation of liquid ammonia under shock conditions up to 1.3 TPa, predicting phase transitions and metallic states.

Findings

Liquid ammonia undergoes a gradual phase transition along the Hugoniot.

At about 4800 K, ammonia becomes a metallic, complex mixture.

Predicted equation of state agrees with experimental data up to 64 GPa.

Abstract

We investigate via quantum molecular-dynamics simulations the thermophysical properties of shocked liquid ammonia up to the pressure 1.3 TPa and temperature 120000 K. The principal Hugoniot is predicted from wide-range equation of state, which agrees well with available experimental measurements up to 64 GPa. Our systematic study of the structural properties demonstrates that liquid ammonia undergoes a gradual phase transition along the Hugoniot. At about 4800 K, the system transforms into a metallic, complex mixture state consisting of $\textnormal{N}\textnormal{H}_{3}$, $\textnormal{N}_{2}$, $\textnormal{H}_{2}$, N, and H. Furthermore, we discuss the implications for the interiors of Uranus and Neptune.