Entropy, disorder, melting

The connection of geometric or spatial disorder and entropy is examined. The formulation of the problem of the entropy of a geometrically disordered system is asserted to make no sense if one does not stipulate the method of preparing it. The nonergodicity of geometrically disordered systems and the conditionality of their thermodynamic analysis are stressed. The relative constancy of the entropy of melting of simple classical substances is explained by the weak dependence of the entropy of a simple liquid on the number of particles involved in collective motion and collectively utilizing the accessible space. Certain features of quantum and low-dimensional systems are discussed.