  The breaking stress (the maximum of the stress-strain curve) of neutron star
crust is important for neutron star physics including pulsar glitches, 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. We describe our
results with the Zhurkov model of strength. We apply this 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
timescales the breaking stress depends strongly on the temperature. For
coupling parameter <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.
