  Adsorption of ortho-deuterium and para-hydrogen films on a graphite
substrate, pre-plated with a single atomic layer of krypton, is studied
theoretically by means of quantum Monte Carlo simulations at low temperature.
Our model explicitly includes substrate corrugation. Energetic and structural
properties of these adsorbed films are computed for a range of hydrogen
coverages. Thermodynamically stable adsorbed films are solid, with no clear
evidence of any liquid-like phase. Quantum exchanges of ortho-deuterium and
para-hydrogen are essentially absent in this system, down to zero temperature;
consequently, this system displays no superfluidity in this limit. Our
simulations provide evidence of a stable domain wall fluid at low temperature,
consistently with recent experimental observations.

Statistical Mechanics