Water-like Anomalies from Repulsive Interactions

Abstract

In tetravalent network materials like quartz or ice the main interactions are the strong bonds that connect each vertex to four others and the repulsive forces that keep non-bonded vertices further apart. Those interactions, modelled by square wells, are shown to be sufficient to account for the stability of ice-like crystals, with tetrahedral bond angles, at low temperature; endothermic melting of the crystal to a denser water-like amorph at intermediate temperatures; exothermic collapse of the supercooled crystals at high pressure, to a glass, without breaking any bonds; expansion on cooling of both the crystal and the amorph; and a line of spinodal instabilities in the water-like supercooled amorph where the compressibility, heat capacity and negative expansivity diverge. © 1998, The Japan Society of High Pressure Science and Technology. All rights reserved.