The breaking stress of neutron star crust is important for neutron star physics including emission of gravitational waves from static mountains and flares from star quakes. We perform many molecular dynamic simulations of the breaking stress at different coupling parameters (inverse temperatures) and strain rates. Our results can be described by the Zhurkov model of strength and we extract parameters describing the effective number of ions and activation energy involved when the crust fails. We apply the Zhurkov model to estimate the breaking stress for timescales ∼ 1 s – 1 year, which are most important for applications, but much longer than can be directly simulated. At these very long timescales the breaking stress depends strongly on temperature. For coupling parameter Γ <∼ 200 matter breaks at very small stress, if it is applied for a few years. This viscoelastic creep can limit the lifetime of mountains on neutron stars. We also suggest an alternative model of timescale-independent breaking stress, which can be used to estimate an upper limit on the breaking stress.

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