  We employed a fully optimized Shadow Wave Function (SWF) in combination with
Variational Monte Carlo techniques to investigate the properties of HD
molecules and molecular ortho-deuterium (o-D_2) in bulk solid para-hydrogen
(p-H_2). Calculations were performed for different concentrations of impurities
ranging from about 1% to 25% at the equilibrium density for the para-hydrogen
crystal. By computing the excess energy both for clustered and isolated
impurities we tried to determine a limit for the solubility of HD and o-D_2 in
p-H_2.
