19 research outputs found
First-principles calculation of the thermal properties of silver
The thermal properties of silver are calculated within the quasi-harmonic
approximation, by using phonon dispersions from density-functional perturbation
theory, and the pseudopotential plane-wave method. The resulting free energy
provides predictions for the temperature dependence of various quantities such
as the equilibrium lattice parameter, the bulk modulus, and the heat capacity.
Our results for the thermal properties are in good agreement with available
experimental data in a wide range of temperatures. As a by-product, we
calculate phonon frequency and Grueneisen parameter dispersion curves which are
also in good agreement with experiment.Comment: 9 pages, 8 figures, submitted to Phys. Rev. B April 30, 1998). Other
related publications can be found at
http://www.rz-berlin.mpg.de/th/paper.htm
Thermodynamic Properties of the One-Dimensional Extended Quantum Compass Model in the Presence of a Transverse Field
The presence of a quantum critical point can significantly affect the
thermodynamic properties of a material at finite temperatures. This is
reflected, e.g., in the entropy landscape S(T; c) in the vicinity of a quantum
critical point, yielding particularly strong variations for varying the tuning
parameter c such as magnetic field. In this work we have studied the
thermodynamic properties of the quantum compass model in the presence of a
transverse field. The specific heat, entropy and cooling rate under an
adiabatic demagnetization process have been calculated. During an adiabatic
(de)magnetization process temperature drops in the vicinity of a field-induced
zero-temperature quantum phase transitions. However close to field-induced
quantum phase transitions we observe a large magnetocaloric effect