Polymerization of sodium-doped liquid nitrogen under pressure

TL;DR

This study uses first-principles molecular dynamics to explore how sodium doping influences the pressure-induced polymerization of liquid nitrogen, revealing stable phases and structural transitions at high pressures.

Contribution

It provides new insights into the structural and thermodynamic behavior of sodium-doped liquid nitrogen under high pressure, a topic not extensively studied before.

Findings

Identification of three local order regions at different pressures

Sodium-doped mixtures are thermodynamically stable above certain pressures

Structural and electronic properties change with pressure and Na concentration

Abstract

First-principles molecular dynamics (FPMD) simulations are performed on 6 and 12% Na in dense liquid N. A detailed description of structural and electronic properties leading to an understanding of the effect of Na-doping on the polymerization phase transition of N is presented. Compression of the mixtures from 5 to 90 GPa shows three distinct regions of characteristic local order separated by pressures near 30 and 65 GPa. Computation of Gibbs free energies of mixing shows that these mixtures are thermodynamically stable beyond 20 and 15 GPa for 6 and 12 % Na respectively.