Ab initio calculations of the equation of state and elastic constants of aluminum in the region of negative pressures

The results of ab initio calculations are presented for the specific energy, pressure, and elastic constants of an aluminum fcc single crystal with subnormal densities at $T=0$. Kinks in the elastic constant vs. density curves are revealed which are caused by the electronic topological transitions. An analysis of the mechanical stability of aluminum fcc crystal at negative pressures suggests that the polymorphic transition to a noncubic structure is possible. A method is suggested for taking into account the thermal nuclear excitation and the influence of zero-point vibrations on the pressure dependence of crystal density.