Contribution of dislocations to the low-temperature heat capacity of crystals
Аннотация
The dislocation contribution to the low-temperature heat capacity of crystals is investigated theoretically. The change produced in the spectral density of the crystal by three basic factors is analyzed in detail: appearance of specific vibrational modes—dislocation phonons—in the vibrational spectrum; the presence of a static elastic field of the dislocations; and, appearance of quasilocal vibrations near dislocations. Expressions for the corresponding components of the dislocation contribution to the heat capacity are derived and analyzed. It was established that when the effect of impurities and Peierls relief are taken into account a complicated nontrivial dependence of this part of the heat capacity on the temperature and the parameters of the problem is obtained. The conditions necessary for observing dislocation effects experimentally are analyzed. The temperatures at which the dislocation contribution can be equal to the heat capacity of an ideal lattice are estimated for a number of substances. It is shown that superconducting metals are suitable for experimental investigations, since in such metals high dislocation densities can be achieved and the electronic part of the heat capacity decreases rapidly with decreasing temperature.