Landau-Placzek ratio for heat density dynamics and its application to heat capacity of liquids.
Exact relation for contributions to heat capacity of liquids is obtained from hydrodynamic theory. It is shown from analysis of the long-wavelength limit of heat density autocorrelation functions that the heat capacity of simple liquids is represented as a sum of two contributions due to "phonon-like" collective excitations and heat relaxation. The ratio of both contributions being the analogy of Landau-Placzek ratio for heat processes depends on the specific heats ratio. The theory of heat density autocorrelation functions in liquids is verified by computer simulations. Molecular dynamics simulations for six liquids having the ratio of specific heats γ in the range 1.1-2.3, were used for evaluation of the heat density autocorrelation functions and predicted Landau-Placzek ratio for heat processes. The dependence of contributions from collective excitations and heat relaxation process to specific heat on γ is shown to be in excellent agreement with the theory.
Institute for Condensed Matter Physics of the National Academy of Sciences of Ukraine, 1 Svientsitskii Street, UA-79011 Lviv, Ukraine.
Taras
T
Bryk
Giancarlo
G
Ruocco
Tullio
T
Scopigno
D001128:Argon / Q000737:chemistry*; D006358:Hot Temperature; D007501:Iron / Q000737:chemistry*; D008094:Lithium / Q000737:chemistry*; D056004:Molecular Dynamics Simulation
D001128:Argon; D008094:Lithium; D007501:Iron