MOLECULAR-DYNAMICS ENSEMBLES - FLUCTUATIONS AND CORRELATIONS NEAR THEPHASE-TRANSITIONS

Computer simulations of liquid and solid systems very close to the mel ting-freezing transition zone have been performed for the microcanonic al, canonical, and isothermal-isobaric molecular-dynamics ensembles. T emperature, pressure, and density fluctuations were studied over long evolution times, and graphical and analytical statistical-error method s were used to investigate correlations in the data. The Nose-Hoover ( NH) method combined with the Toxvaerd algorithm is proposed as a corre ct method of obtaining the true fluctuation and correlation of the the rmodynamic variables in the system, because the temperature and/or pre ssure constraints in the NH method do not affect the dynamical evoluti on of the system, and because the fifth-order Toxvaerd algorithm gives very accurate behavior for the correlations, as has been shown in rec ent studies.