The structure of accreted neutron star crust

TL;DR

This study uses molecular dynamics simulations to reveal the detailed atomic structure of neutron star crusts, highlighting impurity effects on lattice formation, nuclear reactions, and thermal conductivity.

Contribution

It provides the first detailed atomic-scale characterization of neutron star crust structure considering impurity effects using molecular dynamics.

Findings

Neutron star crust forms a body centered cubic lattice despite impurities.

Low Z impurities prefer interstitial sites; high Z impurities prefer substitutional sites.

Impurities significantly influence nuclear reaction rates and thermal conductivity.

Abstract

Using molecular dynamics simulations, we determine the structure of neutron star crust made of rapid proton capture nucleosynthesis material. We find a regular body centered cubic lattice, even with the large number of impurities that are present. Low charge $Z$ impurities tend to occupy interstitial positions, while high $Z$ impurities tend to occupy substitutional lattice sites. We find strong attractive correlations between low $Z$ impurities that could significantly increase the rate of pycnonuclear (density driven) nuclear reactions. The thermal conductivity is significantly reduced by electron impurity scattering. Our results will be used in future work to study the effects of impurities on mechanical properties such as the shear modulus and breaking strain.