Mechanical properties of simple condensed matter

Many mechanical properties of glasses and liquids, such as the large shear susceptibility compared to the compressibility, seem strange and unexpected. However, they are basically the same as those found for irradiated crystals at low defect concentrations. This finding is predicted by the Interstitialcy Theory of Condensed Matter (ITCM). According to the ITCM, a liquid is a crystal containing a few percent of interstitialcies (dumbbell configuration), while a glass is a frozen liquid. Recent computer simulations have supported this assertion. Among thermodynamic properties, changes of the shear modulus G and entropy S play a key role in explaining the physics of condensed matter. The sensitivity of measured shear modulus changes is typically about four orders of magnitude greater than that of the entropy. Simple mechanical models can be given for the mechanical properties. The large entropy of melting of the elements provides a proof that the agents of melting are interstitialcies. Shear modulus measurements provide strong evidence for the ITCM.