Anomalous specific heat of solid deuterium below 0.6 K

An anomaly has been observed in measurements of the specific heat at saturated vapor pressureC _s of pure, solid D₂ of low para-D₂ concentration below0.6 K. The new anomaly has been interpreted as evidence for the significance of electric quadrupole-quadrupole interaction between next-nearest-neighbor pairs of para-D₂ molecules.     

Anomalous specific heat of liquid 3He above the superfluid transition temperature

The contribution to the specific heat due to order parameter fluctuations in liquid ³He just above the superfluid transition temperature T _c is calculated exactly within a Landau theory approach. The effect turns out to be unobservably small and thus cannot explain the large (9%) rise in specific heat above the normal state value at the saturated vapor pressure in a recently reported experiment. We do not find the divergence of the specific heat at T cobtained earlier by Thouless from a microscopic calculation and indicate how the difference can be reconciled.     

Anomalous specific heat of 3He in 4He-coated FSM-16 mesopores

No Heading Recent experiments have found unusual behavior of the specific heat of ³He-⁴He mixtures within the regular porous material FSM-16. We analyze this problem with quantum density functional calculations of ⁴He, followed by ideal gas calculations of ³He in the resulting potential. The results are in semiquantitative agreement with the experimental data.PACS 67.40.–w 67.70.+n     

Isochoric specific heat in the methane-ethane system around the liquid-gas critical line

Experimental and theoretical studies have been made on the behavior of the isochoric specific heat for binary methane-ethane mixtures in the critical region.     

Temperature dependence of the specific heat and thermodynamic functions of alloys of the Pb-Ca system

Investigation results for the temperature dependence of the specific heat and thermodynamic functions of lead-calcium alloys are represented.     

Nuclear specific heat of thallium

We have measured the nuclear specific heat of a 0.79 mole thallium sample of 5 N+ purity in the temperature range 70 µKT20 mK and in magnetic fields from 20 mTB228 mT. The experimental results agree with the theoretical expectation for the specific heat of a nuclear paramagnet with the properties of Tl. Our results for the nuclear specific heat imply that the static properties of bulk Tl seem to differ from the dynamic, surface-sensitive properties of Tl samples investigated in former nuclear magnetic resonance experiments.     

Anharmonic effects in the specific heat of aluminum

The specific heat at constant pressure, C _p , of aluminum has been measured by Leadbetter between 300 and 772 K and by Brooks and Bingham between 330 and 893 K. Both sets of data are converted to the specific heat at constant 0 K volume, C _v0, by the Slater-Overton method, based on the equation of state and not the Debye type of theory. Corrections to the work of Overton are given. Our analysis shows that the C _v0 obtained from Leadbetter's data remains below 3R up to 750 K, whereas it becomes >3R for the Brooks and Bingham data in the temperature range 650–850 K. Calculations of C _v0 (harmonic + anharmonic) from three pseudopotentials are reported for (a) Harrison modified point ion potential with Hubbard exchange and correlation factor in the dielectric function, (q); (b) Ashcroft pseudopotential with the same (q) as in (a); and (c) Dagens-Rasolt-Taylor (DRT) M2 pseudopotential with Geldart-Taylor (q). The shape of the C _v0 curve is found to be similar for all three potentials. For DRT potential, C _v0 reaches 3R at 700 K, whereas the other two barely approach 3R about 900 K. The anharmonic contribution to C _v0 is a factor of two larger for the Dagens et al. compared to the other two potentials. There is a marked difference between the C _v0 curve from the analysis of the Brooks and Bingham data and the theoretical curves. It appears that the experimental points are too high from about 500 K up. The C _v0 curve from Leadbetter's data is very similar to the three theoretical curves, but the results appear to be too low. A remeasurement of the specific heat from 500 K to the melting point is needed.     

The specific heat of solid oxygen

Measurements have been made in the temperature range from 1.3° K to about 71°K with particular attention to the behavior at very low temperatures, and in the neighborhood of the - transition at about 23.89° K. Assuming that near 0° K each molecule moves as a single mass point with the passage of lattice waves, the effective Debye temperature at 0° K is extrapolated to be 104±2° K. As the temperature rises above 10° K, the specific heat rises more rapidly than a reasonable Debye model would predict, suggesting the appearance of additional degrees of freedom, which are thought to be the superposition of a librational motion of the molecules superposed on the longitudinal and transverse lattice waves controlling the motion of a molecule's center of mass. The specific heat shows a very sharp high spike at the - transition with an entropy change of aboutR ln 1.65; there is no evidence for a latent heat associated with this transition.     

Constant-volume specific heat of solid xenon

Specific heats of solid xenon were measured between 110 and 223 K in a closed pressure vessel. In this temperature interval the pressure increased from the vapor pressure of the solid at 110 K to about 1.7 kbar at the melting point. After a small correction for the nonrigidity of the container, we find that c_v increases from 2.9R at 110 K to the classical Dulong-Petit value of 3R at 200 K. The behavior of the specific heat in the vicinity of the melting point depended on the treatment of the samples.Research supported by the National Science Foundation. This paper is based on a thesis submitted to the Graduate Faculty of Rutgers University in partial fulfillment of the requirements for the PhD degree.     

Low-temperature specific heat of layered compounds

Specific heat measurements in the temperature range from 1 to 10 K and in magnetic fields up to 1.2 T have been made on a number of layered transition metal dichalcogenide crystal complexes. The thermodynamic critical fieldH _c and the Ginzburg-Landau coherence length and penetration depth have been calculated. For TaS₂ (pyridine)_1/2 and TaS_1.6Se_0.4 (pyridine)_1/2, the coherence length perpendicular to the layers is slightly less than the interlayer separation.Research at Stanford supported by Air Force Office of Scientific Research, Air Force Systems Command, USAF, under grant AFOSR 73-2435B.     

Constant-volume specific heat of solid argon

Specific heats of solid argon were measured between 25 K and 120 K in a closed pressure vessel. Between 60 K and the melting point of 120 K the solid filled the vessel, and at the m.p. the pressure was 1.6 kbar. After correction for the nonrigidity of the container, we find thatC _v increases by 7.3% between 60 K and 120 K, reaching 2.8 R. Comparison with recent calculations based on self-consistent phonon theory reveals substantial discrepancies from the data, indicating the necessity of including higher-order terms in the theory.Research supported by the National Science Foundation and the Rutgers University Research Council.     

Very-low temperature specific heat of Torlon

The specific heat of Torlon has been measured in the 0.15-4.2 K temperature range. Data below 1 K can be represented by c(T) = P₁T^1+δ + P₂T³, with P₁ = (5.41 ± 0.08)·10⁻⁶J K^−(2+δ) g⁻¹, P₂ = (2.82 ± 0.03) ·10⁻⁵JK⁻⁴g⁻¹ and δ = 0.28 ± 0.01, as predicted by the tunnelling theory. Above 1 K, the behaviour of c(T) is similar to that of other amorphous materials and can be expressed as: c(T) = P · T^Ω with P = (2.68 ± 0.07)·10⁻⁵JK^Ω+1g⁻¹ and Ω = 3.32 ± 0.02.     

Low-temperature specific heat of high-purity calcium

Low-temperature specific heat of high-purity calcium has been measured with an adiabatic calorimeter with a mechanical heat switch to avoid helium exchange gas errors, over the temperature range 1.1–4.2 K. The values obtained for the electronic coefficient of specific heat and the Debye temperature _D are =1.99±0.05 mJ/moleK ² and _D=250±4K.     

Low-temperature specific heat of Ti-Hf alloys

The effect of alloying on the specific heat of Ti-Hf alloys has been investigated in the temperature range 1.2–4.5 K. A maximum is observed in the electronic specific heat coefficient γ around 35 at % Ti and the Debye temperature θ _D decreases from titanium to hafnium. No superconductivity is found down to the lowest temperature studied.     

Experimental investigation of the specific heat of potassium vapor

The specific heat c_p of potassium vapor has been measured by means of a continuous-flow calorimeter in a circulation loop. The results are used to determine the dissociation energy of the K₂ molecule.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 15, No. 5, pp. 893–898, November, 1968.     

Phonon softening on the specific heat of nanocrystalline metals

Specific heat enhancement in several common nanocrystalline metals is established by comparison with their bulk counterparts. Measurements were carried out in Fe, Cu, Ni and binary alloy LaAl(2). The excess specific heat is evidenced as a low temperature peak below 65 K and a high temperature slope above 150 K. The experimental data are in good agreement with a model which considers contributions from the grain boundary and core atoms in the nanoparticles. This model is supported by Raman spectroscopy measurements, showing a softening of the frequency phonon modes associated with a size reduction and increase of the atomic disorder.     

Comment on the specific heat of superfluid 3He

We present numerical results for the specific heat of ³He-B in the weak-coupling-plus model. We find that the full temperature dependence of the specific heat is accurately determined by the specific heat jump at T _c .This provides a test of the T _c /T _F expansion scheme for calculating strong coupling effects in superfluid ³He.