PC-based automated setup for measuring the isochoric heat capacity of liquids

A setup formeasuring the isochoric heat capacity of liquids and gases and its automation method based on a Keithley 2000 digital multimeter and a personal computer are described. The program development in the Labview 7 environment is considered. The experimental measurement method itself is also briefly described.     

Anomalously high heat capacity of liquids: relation to structural properties

ABSTRACT

Heat capacity of several liquids which demonstrate anomalous behaviour is studied. It is shown that isochoric heat capacity of these liquids shows anomalously high values which is related to smooth structural crossover in these liquids. This phenomenon can be used for qualitative explanation of high heat capacity of water and some other substances.     

On the specific heat of Fermi liquids

The contributions of long-wavelength spin fluctuations to the specific heat of Fermi liquids is consistently calculated on the basis of the Landau theory of Fermi liquids. More satisfactory estimations of the Landau parameter F₁^a for liquid ³He are obtained.     

On the specific heat of fermi liquids

The spin fluctuation contribution to theT ³ logT term in the specific heat of nearly ferromagnetic Fermi liquids is evaluted again. A result different from^1,2 is found, which in the case of liquid Helium agrees better with experiment.     

用力敏传感器测量液体表面张力系数

利用力敏传感器测量液体表面张力系数，既改进了传统的实验方法和仪器，提高了实验的准确度和稳定性，同时因实现了非电量电测，也有助于测量过程中学生对物理过程的观察和规律的理解。     

Low-temperature heat capacity of metals

The low-temperature heat capacities of transition metals and alloys were reviewed by Heiniger, Bucher, and Muller¹ in 1966, with particular emphasis on the dependence of the electronic heat capacity on the number of conduction electrons. Nuclear contributions to the heat capacity of metals and alloys have been reviewed recently by Lounasmaa.² The most recent general review of the low-temperature heat capacities of metals, however, was that by Keesom and Pearlman³ in 1956. Since that time there have been important advances in experimental techniques and also in theory related to certain of the heat capacity contributions.     

Electronic heat capacity of bismuth

The observed electronic heat capacity of bismuth is found to be in better agreement with the values calculated on the ellipsoidal nonparabolic (ENP) model than on the ellipsoidal parabolic (EP) model. Values of γ obtained experimentally and from the ENP model are 8.5 ± 1.5 and 8.28 respectively while the EP model gives 6.8 (from Kao's parameters) and 5.0 (from Williams, and Smith et al. parameters).     

Anomalous heat capacity of nanoparticles

It was shown experimentally that the specific heat of nanosized particles was higher than that of macroscopic particles of the same nature. It was also found that the heat capacity increased as the size of nanoparticles decreased. We analyzed the reasons for the anomalous behavior of the heat capacity of nanoparticles. For this purpose, we considered nanoparticles with a simple cubic lattice and an arbitrary external geometric shape. The simplest harmonic interaction potential between the nearest neighbor particles was used. Qualitative agreement with experimental data was obtained. The main factor responsible for the anomalous behavior of small particles was phonon spectrum softening compared with bulk material when free boundary conditions were used. The lower frequencies make a larger contribution to heat capacity. It was found that, apart from particle size, the geometric shape and defect structure of nanoparticles influenced their heat capacity: given the same number of particles, an increase in asymmetry and disorder caused an increase in heat capacity.     

用等厚干涉测液体的折射率

在等厚干涉的实验中,加入了用劈尖干涉对比法测液体折射率的内容,在不改变劈尖膜的条件下,同时测得空气膜和液体膜的干涉条纹宽度,从而可方便地求出液体的折射率,也使得等厚干涉的实验内容更加丰富和充实．     

High-temperature heat capacity of the BiFeO3 multiferroic

Data on the heat capacity of the BiFeO₃ multiferroic have been obtained within a broad temperature interval. Correlation has been established between the composition of the Bi₂O₃-Fe₂O₃ pseudobinary system and the specific heat capacity of the oxide compounds.     

Physical contributions to the heat capacity of nickel

Heat capacity data for solid nickel have been re-evaluated and analyzed into physical contributions, 0–1726 K. Two new sets of measurements of C_p(Ni), 333–1500 K, have been combined with literature data to produce an evaluated data set with uncertainty ? ± 2%. These smoothed data have been analyzed into vibrational harmonic, electronic, magnetic and dilatational contributions with the aid of auxiliary measurements of expansion coefficient, compressibility, vibrational and electronic densities of states, elastic constants, and magnetic exchange integral and susceptibility obtained from the literature. The vibrational harmonic term is interpreted in terms of a θ_D-vs-T curve in accord with predictions of the density-of-states distribution. The electronic contribution is smaller than predicted by free-electron theory due to a large electron-phonon effect. The electronic term for paramagnetic nickel is in good agreement with that predicted from band calculations. The magnetic contribution yields a magnetic entropy in accord with theoretical predictions, and a magnetic internal energy and critical-point behavior in agreement with the isotropic Heisenberg model. The experimental heat capacity can be accounted for without reference to vibrational anharmonic and vacancy contributions, in accord with recent calculations.     

Classical fluids of negative heat capacity

It is shown that new parametersX can be defined such that the heat capacity C_xT(S/T)_x is negative, even when the canonical ensemble [i.e., at fixed T=(U/S)_Y and YX] is stable. This implies an extension of the classical theory of polytropes from ideal gases to general fluids. As examples of negative heat capacity systems we treat blackbody radiation and general gas systems with nonsingular _T. For the case of a simple ideal gas we even exhibit an apparatus which enforces a constraint X(p, V)=const that makes C_x<0. We then show that it is possible to infer the statistical mechanics of canonicallyunstable systems-for which even the traditional heat capacities are negative-by imposing constraints that stabilize the associated noncanonical ensembles. Two explicit models are discussed.     

Time-dependent heat capacity of water-lysozyme solution

Summary We report here the first observation of the time-dependent heat capacity of water-lysozyme solution. The observed increase of heat capacity in time occurs independently of the lysozyme concentration and thepH value of the solvent. The time necessary to attain the heat capacity equilibrium value and the amplitude of the effect are not well reproducible; the former tends to increase with temperature, while the amplitude decreases and practically disappears about 35°C. Evolution of a spatial order of the proteins in water and/or of water molecules interacting with the proteins is considered as a possible explanation for the results. The phenomenon promises to be an important tool to study the role of water in biological organization and activity.     

Low-temperature heat capacity of rare-earth tetraborides

The paper reports an experimental study of the temperature dependences of the heat capacity of tetraborides of lanthanum, dysprosium, holmium, and lutetium in the range 2–300 K. The electronic, lattice, and magnetic contributions to the total heat capacity of the borides have been identified and analyzed, and the Schottky contribution has been calculated. The ground-state multiplicities of dysprosium and holmium ions in the tetraborides have been determined.     

Low-temperature heat capacity and heat conductivity of single-crystal synthetic opals

The heat capacity at constant pressure (in the range 3–50 K) and the lattice heat conductivity (from 5 to 75 K) of a single-crystal synthetic opal are measured. It is shown that the heat capacity of the opal behaves at these temperatures in a way similar to porous amorphous materials. The data on the heat conductivity suggest that single-crystal opals can be related to a class of semicrystalline (partially crystallized amorphous) materials. However, because of specific features of their crystal structure, the opals form a nonstandard type of semicrystalline material which we termed semiamorphous.     

Critical behavior of the heat capacity of Ag-doped manganites

The critical behavior of the heat capacity of silver-doped manganites has been studied. The laws of variation in the universal critical parameters near the phase transition point have been established. It has been shown that the universality class of the critical behavior of the heat capacity for the La_1−x Ag _y MnO₃ (y≤x) system does not depend on the silver concentration or the synthesis conditions.     

气体的摩尔热容量随温度变化的实验研究

采用压力传感器和温度传感器,通过数据接口由计算机实时采集数据并进行处理,观察到气体的热力学过程的状态变化,测得了氧气的摩尔热容量CV随着温度的变化.结果表明氧气的CV随温度的变化有一突变,这与能量均分定理所描述的基本一致,氧气的振动自由度被冻结的温度在240K左右.     

Components of the low-temperature heat capacity of rare-earth hexaborides

The temperature dependence of heat capacity C _p(T) was studied for nine rare-earth hexaborides MB₆(M=La, Ce, Pr, Nd, Sm, Eu, Gd, Tb, and Dy) at temperatures of 5–300 K. Using the correspondence principle for lattice heat capacities of isostructural compounds, the lattice contribution C ₁(T) and the excess contribution ΔC(T) to the heat capacity of the hexaborides were determined. The lattice heat capacity C ₁(T) is represented as the sum of the Debye contributions of the metal and boron sublattices: C ₁(T)=C _M (T)+6C _B(T). The Debye temperatures π_M and π_B of the metal and boron sublattices were determined. The anomalies in the excess heat capacity ΔC(T)=C _p (T)?C ₁(T) are related to the magnetic ordering effects, the Schottky contribution, and the Jahn-Teller effect.     

Low temperature heat capacity of Rh-Cu alloys

Reported here are the low temperature heat capacity data on a series of single phase fcc Rh-Cu alloys. The electronic heat capacity coefficient, γ, decreases rapidly up to 20 at % of copper in Rh and then stays constant to ～60 at % Cu after which decreases smoothly to the pure Cu value. This is interpreted as due to the initial partial filling of the d-band after which the conduction electron of Cu goes into the s-band. An attempt is made to understand the origins of the curious anomalies in the Debye temperature and microhardness data.