Elastic Waves and the Thermal Capacity of a Crystal
Dulong and Petit in 1819 discovered the rule that the atomic thermal capacity of any solid is 6 cal/deg. This rule agrees well with experiment for suitable high temperatures, and classical statistical physics readily explains it by considering each atom as a threedimensional harmonic oscillator with quasielastic binding to some equilibrium position, the distribution of the energy over the degrees of freedom being invoked. This distribution indicates that each degree of freedom at equilibrium has the same energy kT/2, in which T is absolute temperature and k is Boltzmann’s constant, which is 1.38044 × 10-16 erg/deg.
KeywordsElastic Wave Debye Temperature Barium Titanate Hexagonal Crystal Proper Mode
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