  We calculate the energy deposition by very short laser pulses in SiO_2
(alpha-quartz) with a view to establishing systematics for predicting damage
and nanoparticle production. The theoretical framework is time-dependent
density functional theory, implemented by the real-time method in a multiscale
representation. For the most realistic simulations we employ a meta-GGA
Kohn-Sham potential similar to that of Becke and Johnson. We find that the
deposited energy in the medium can be accurately modeled as a function of the
local electromagnetic pulse fluence. The energy-deposition function can in turn
be quite well fitted to the strong-field Keldysh formula for a range of
intensities from below the melting threshold to well beyond the ablation
threshold. We find reasonable agreement between the damage threshold and the
energy required to melt the substrate. The ablation threshold estimated by the
energy to convert the substrate to an atomic fluid is higher than the
measurement, indicating significance of nonthermal nature of the process. A
fair agreement is found for the depth of the ablation.
