Structure-energy map of alkali borosilicate glasses: Effects of pressure and temperature

A study of thermodynamic properties and structure of sodium borosilicate glasses with a range of pressure-temperature histories is presented. It is demonstrated how differences in the pressure-temperature path of the liquid during cooling may result in glasses with identical short-range structure and molar volume but different potential energies and, thus, different mid- or long-range structures. Rates of changes of molar volume, excess enthalpy, and boron coordination with changing fictive pressure and fictive temperature are reported. A structure-energy map is given, and paths for transitions under constant pressure, as well as between different pressures are shown. It is shown for pressures between atmospheric and 500 MPa that similar rates of cooling produce similar relative variations in fictive temperature in boron coordination environment and in the potential energy as compared to a given reference state. These results indicate that the rate of configurational entropy generation is independent of pressure in this range.