Aluminum. II. Derivation of C v0from C p and comparison to C v0 calculated from anharmonic models

Turn off the lab furnace and boot up the mainframe

“…More recently, in 2004, Forsblom et al 17 calculated the explicit anharmonicity contribution to the fixed volume heat capacity employing an embedded atom method. Their results show, in contrast to the study by Shukla et al, 16 that the contribution due to explicit anharmonicity can well be of a magnitude similar to the one obtained for the vacancy contribution by Shukla et al 16 The precise value could not be assessed since it varied significantly between the used potential parametrizations. …”

“…With the fully ab initio calculated results at hand, we have a reference against which the performance or accuracy of previously suggested empirical approaches to estimate the effect of vacancies can be tested. One such empirical estimation 16 starts from the following expression for the vacancy contribution to the vacancy heat capacity C…”

“…Reducing the experimental heat capacity from constant pressure to fixed volume and employing a Debye model, the authors interpreted the nonlinear increase in their experimental data as arising mainly from explicit anharmonicity. In 1985, Ditmars et al 6 measured the enthalpy of aluminum by means of isothermal phase-change calorimetry and Shukla et al 16 calculated from these results the isobaric heat capacity. Shukla et al 16 then employed the same reduction scheme as Brooks and Bingham 5 to obtain the fixed volume heat capacity.…”

“…In 1985, Ditmars et al 6 measured the enthalpy of aluminum by means of isothermal phase-change calorimetry and Shukla et al 16 calculated from these results the isobaric heat capacity. Shukla et al 16 then employed the same reduction scheme as Brooks and Bingham 5 to obtain the fixed volume heat capacity. In a subsequent theoretical analysis, they went beyond the Brooks-Bingham approach 5 by employing empirical potentials rather than a simple Debye model to calculate the fixed volume heat capacity.…”

Phonons in aluminum at high temperatures studied by inelastic neutron scattering

“…More generally, understanding the contributions of quasiparticles and collective excitations to the free energy, entropy, and heat capacity of crystalline solids is an active area of research. 17,[35][36][37][38][39][40][41][42][43][44] Here we present results from inelastic neutron scattering measurements of the phonon DOS of aluminum at temperatures of 10, 150, 300, 525, and 775 K. We use these results to determine the phonon contributions to the entropy of aluminum, and we assess the other entropic contributions, finally obtaining excellent agreement with the total thermodynamic entropy. The overall softening of the phonons is found to be caused by a monotonic temperature dependence of the first nearest-neighbor ͑1NN͒, second nearest-neighbor ͑2NN͒, and third nearest-neighbor ͑3NN͒ force constants, with the 1NN force constants decreasing approximately 10% over the temperature range of measurement.…”