Molecular Dynamics Simulations of Accreting Neutron Star Crust

Material accreting on a neutron star can undergo rapid proton capture nucleosynthesis to produce a variety of nuclei up to mass numbers around 100. This complex rp ash then undergoes electron capture as it is buried to higher densities. We perform molecular dynamics simulations to determine how this material freezes to form new neutron star crust. In addition, from our simulations we calculate many properties of crust made of this complex rp ash composition including thermal conductivity, viscosity, and shear modulus. We also calculate the strong screening enhancement of nuclear reaction rates. Finally, we are determining the breaking strain (strength) of the crust. This is important for the height of mountains that radiate gravitational waves and may be important for giant flares (extremely energetic gamma / X-ray bursts) from very strongly magnetized neutron stars called Magnetars. These flares may originate in a star quake when magnetic stress breaks the crust.