Systems with a 1:1 composition of nitric acid and water were investigated using ab initio quantum chemical methods. We found that the optimized geometry of the complex of a nitric acid and a water molecule is quasi planar with one hydrogen pointing out of the plane. Structural and vibrational data are presented for this complex. We optimized the ionic positions of the bulk and the (100) surface of nitric acid monohydrate crystal using ab initio molecular dynamics with simulated annealing. Some features of the systems and trials of adsorbing HCl, ClONO2, and H2O on the surface are presented. We did not find specific adsorption that may imply the catalytic effect of the perfect surface on the reactions involved in the depletion of ozone. The systems remained stable during ab initio molecular dynamics performed around 195 K. The only observed change was the reversible proton transfer among the oxonium and nitrate ions in the crystal.