On the nature of the tensile instability in metastable liquids and its relationship to density anomalies

Tensile instability is a hitherto unexplained phenomenon whereby a metastable liquid loses tensile strength as the temperature is reduced in the vicinity of its triple point. The thermodynamically consistent behavior which must be exhibited by any liquid in the vicinity of a tensile instability displays a variety of unusual phenomena: nonanalytic density maxima, spinodal retracing, and density anomalies (negative thermal expansion coefficient) in the vicinity of the spinodal curve. Loss of tensile strength implies (and is inseparable from) density anomalies in the vicinity of the spinodal curve. This important conclusion is derived here from first principles.