A Quantum Monte Carlo Study On Confined Hydrogen Isotope Molecular

In this thesis,we systematically summarized the studies on compress hydrogen,and introduced widely used theoretical methods,especially the Monte Carlo method,which we used in this work.We used revised hard sphere model to study different hydrogen isotopes under compress.We used Monte Carlo method numerical simulated a protrium/deutrium molecule in a hard ellipsoid box,and then achieved the status of molecular under pressure.We find that:1.We found the phase border between phase ? and phase ? of hydrogen,and proofed that deutriun undergoes the same phase transition at higher pressure,and tested the isotope difference.2.We found some numerical relation:For a certain isotope molecule at a certain phase,totel energy and pressure is linear to the mole density,and the bond length is exponential to the pressure.3.The nuclear kinetic energy of both isotopes are about 1/1000 of electron's kinetic energy.For protium,there is a potential relation between the kinetic energy and pressure,while for deuterium it much complex.4.There might be an phase transition introduced by the vary of length changing rate.And there is an anomalous elongation of deutrium's bondlength.5.There is a cliff change of the ratio between the average step length of nucleus and that of electron at about 350 GPa,which might indicate the phase transition between Phase III and the phase after it.Our work may contribute to the understanding of isotope effect,the equation of state of hydrogen at pressure,and to evaluate the influence of non-electron-phonon-effect in other simulations.