Two universal equations of state for solids satisfying the limiting condition at high pressure

In this paper it is shown that the relationship of bulk modulus with pressure, B=f(P), should be linear both at low and high-pressure limiting conditions. Because most of present equations of state (EOS) for solids cannot satisfy such linear relationship at high pressure, a new function f(P) is proposed to satisfy the linearity. By integrating the bulk modulus, an EOS with three parameters and satisfying the quantum-statistics limitation is derived. It is shown that the EOS can be reduced to two-parameter EOS approximately satisfying the limiting condition. By applying the two EOSs and other three typical EOSs to 50 materials, it is concluded that for materials at low and middle-pressure regimes, the limiting condition does not operate, the Baonza EOS gives the best results, but it cannot provide analytic expression for cohesive energy. The Vinet and our second EOSs are slightly inferior, both EOSs can provide analytic expression for cohesive energy, and for materials at high-pressure regimes our second EOS gives the best results. The Holzapfel and our first EOSs give the worst results, although they strictly satisfy the limiting condition. For practical applications, the limiting condition is not important because it only operates as V→0.     

Obtention des bandes de cameron par photo excitation de co en matrices d'argon de krypton et de xenon

CO trapped in solid matrices of argon, krypton and xenon has been excited by 10 eV photons. Cameron bands v′=0, v″=0,1,2,3,4 are observed during the irradiation. If red shifts are observed in argon and krypton matrices, the transition in xenon shows no differences with gas phase data.     

Vacancy-induced heat transfer in solid Kr and Ar

We have measured constant-volume thermal conductivities of solid krypton at six molar volumes between 28.84 and 29.54 cm³ mole^?1 and of solid argon at a molar volume of 24.30 cm³ mole^?1 at temperatures of order and above the respective Debye temperatures. An excess thermal conductivity above that following from the T^? law is ascribed to an additional energy flux carried over by vacancies. The estimated activation energy Q_P for self-diffusion derived from the constant-volume values Q_V as determined from the temperature dependences of the “excess” thermal conductivities are in good agreement with the available data of direct diffusion measurements in solid Ar and Kr.     

Constant volume specific heat at constant volume and at zero pressure volume

Using an Improved Self-Consistent Phonon calculation including three phonon processes, the difference between the constant volume specific heat at constant volume (C_υ(T, V_O)) and at zero pressure volume (C_υ(T, V(T))) is shown for the inert gas solids.     

On the law of corresponding states for thermodynamic properties of a crystal

To study thermodynamic similarity of the properties of crystalline substances, we propose an approach connected with engaging of the metastable state region. Internal pressure and specific volume on the crystal’s stability boundary at T = 0 K are used as characteristic scales of thermodynamic variables. A semiempirical method of calculation of the stability boundary by the thermodynamic data related to the stable states region of a solid body is described. In the cases of argon and natrium, the stability boundary is calculated for a wide range of temperatures and pressures. Analysis of the properties of neon, argon, krypton, and xenon crystals in these variables indicates that the law of corresponding states holds for these substances.     

Coexistence of non-registered monolayer and bilayer solid films: Statistical mechanics

A statistical mechanical theory is developed for low temperature solid monolayer and bilayer films of inert gases which are not in registry with the adsorbing substrate. The free energy is evaluated in terms of harmonic lattice vibrations of the solids, which is a quasiharmonic approximation. The lattice constant discontinuity in the transition under compression from the monolayer to the bilayer is found to be small, in accord with experiments on the adsorption of xenon and of krypton on silver and of argon on basal plane graphite. The calculations use realistic models for adatom interactions and substrate holding potentials in these three systems. At the bilayer formation, the lattice constant is still distinctly larger than that of the corresponding bulk solid under its vapor pressure. Thermodynamic functions of the phases at monolayer and bilayer coexistence are evaluated: the spreading pressure and the bilayer latent heat of adsorption are nearly constant along the coexistence curve for temperatures of 1 to 35 K. The calculated difference between the latent heats of adsorption of the monolayer and the bilayer is in good agreement with experimental data for the xenon/silver system, but it is smaller than the experimental difference for the krypton/silver and argon/graphite systems.     

Simulated equation of state of CaF2 with fluorite-type structure at high temperature and high pressure

The pressure-volume-temperature (P-V-T) equation of state (EOS), isothermal bulk modulus, and thermal expansivity of CaF₂ with cubic fluorite-type structure are investigated using the constant temperature and pressure shell model molecular dynamics (MD) method with effective pair potentials which consist of the Coulomb, dispersion, and repulsion interaction. It was shown that MD simulation is very successful in accurately reproducing the measured volumes of the CaF₂ over a wide range of pressures. The simulated P-V data matched X-ray diffraction experimental results up to 9.5 GPa at 300 K. In addition, volume thermal-expansion coefficient and isothermal bulk modulus were also calculated and compared with available experimental data and the latest theoretical results at ambient condition. At extended temperature and pressure ranges, The P-V EOS under different isotherms at selected temperatures, T-V EOS under different isobars at selected pressures, thermal expansivity, and isothermal bulk modulus were predicted up to 1500 K and 10 GPa. The detailed knowledge of thermodynamic behavior and EOS at extreme conditions are of fundamental importance to the understanding of the physical properties of CaF₂.     

On three body forces in rare gas crystals

The effect of three body v.d. Waals forces on the elastic constants of solid argon, krypton and xenon is calculated. It is pointed out that three body forces and zero-point motion have the opposite effect on the violation of the Cauchy relationc ₁₂=c ₄₄. Due to three body forces the quantitityδ=c ₄₄?c ₁₂/c ₁₂ is changed from about +4 to ?4% for argon, while in the case of xenonδ is shifted from + 1 to ?9%.     

Emission characteristics of pulse-periodic barrier-discharge plasma in a mixture of krypton with argon and liquid freon vapor

Radiation of a nanosecond barrier discharge in a mixture of krypton, argon, and carbon-tetrachloride vapor is studied in the spectral range of 150–300 nm. The plasma radiation spectra and the dependences of the intensities of the 258 nm Cl₂(D′ → A′), 222 nm KrCl(B → X), and 175 nm ArCl(B → X) bands on the partial pressure of liquid freon vapor, argon, and krypton, as well as on the discharge excitation conditions, are studied. The optimal compositions of gas mixtures for creating a broadband UV-VUV emitter based on the band system of argon chloride, krypton chloride, and chlorine molecule are determined.     

Monte Carlo simulations of thermodynamic properties of argon,krypton and xenon in liquid and gas state using new ab initio pair potentials

The internal energies and compressibility factors of argon, krypton and xenon have been simulated using recent state-of-the-art ab initio pair intermolecular potentials and the best semi-empirical pair potentials, and the Axilrod-Teller-Muto three-body term. The results are compared with experimental data for both sub-critical and super-critical temperatures and for densities ranging up to a 2.5 multiple of the critical density. Both the ab initio and semi-empirical results for argon are in very good agreement with the experimental ones. For krypton and xenon, the ab initio results are worse than the semi-empirical results but they are still acceptable.     

Elastic, thermal and structural properties of platinum

The thermal equation of state (EOS) for platinum has been calculated to 300 GPa and 3000 K using ab initio molecular dynamics employing the local density approximation (LDA) and the projector augmented-wave methods (PAW). Direct ab initio molecular dynamics avoids the simplifying assumptions inherent in empirical treatments of thermoelasticity. A third-order Birch-Murnaghan equation EOS fitted to the 300 K data yielded an isothermal bulk modulus of B_T0=290.8 GPa and a pressure derivative of B_T′=5.11, which are in better agreement with the measured values than those obtained by previous calculations. The high-temperature data were fitted to a thermal pressure EOS and a Mie-Grüneisen-Debye EOS. The resulting calculated thermal expansion coefficient, α₀, temperature derivative of the isothermal bulk modulus, (∂B_T/∂T)_V, and second temperature derivative of the pressure, (∂²P/∂T²)_V, were 1.94×10⁻⁵ K⁻¹, −0.0038 GPa K⁻¹, and 1.7×10⁻⁷ GPa² K⁻², respectively. A fit to the Mie-Grüneisen-Debye EOS yielded values for the Grüneisen parameter, γ₀, and its volume dependence parameter, q, of 2.18 and 1.75, respectively. An analysis of our data revealed a strong volume dependence of the thermal pressure of platinum. We also present a qualitative analysis of the effects of intrinsic anharmonicity from the calculated Grüneisen parameter at high temperatures.     

Temperature dependence of foreign gas broadening of HCl fundamental lines

A long-pathlength variable temperature cell has been used to study three hydrogen chloride 0–1 vibration-rotational lines, P(7), P(8), and P(9) which were broadened by He, Ar, N₂, O₂, and CO at room temperature and by Ar at low temperatures down to 190 K. The method employed to extract the linewidths is the equivalent width method. The temperature dependence of the resulting cross sections for the HClAr broadened lines is similar to that recently found for other argon broadened HCl infrared and microwave lines. The results reported here (for high J lines) complement the other results (for low J lines) and together seem to constitute enough new data for further theoretical attempts at describing the process of collisional broadening in general, and the broadening of HCl by argon in particular.     

Compression dependence of αKT for ionic solids

In the present study, the compression dependence of αK_T is analyzed using Anderson-Isaak equation along with Stacey's equation of state for ionic solids such as NaCl and MgO. It is found that the value of αK_T decreases with increasing compression and attains a minimum, after which it increases with increasing compression along an isotherm. It is also found that αK_T tends to infinity as P→∞ or V→0. The presented nature of αK_T is valuable to understand the thermoelastic and thermodynamic properties of MgO and NaCl at high compressions and at high temperatures.     

Thermal conductivity of the SiC/Si biomorphic composite, a new cellular ecoceramic

The thermal conductivity κ and electrical resistivity ρ of a SiC/Si biomorphic composite were measured at temperatures T = 5–300 K. The composite is a cellular ecoceramic fabricated by infiltrating molten Si into the channels of a cellular carbon matrix prepared via pyrolysis of wood (white eucalyptus) in an argon ambient. The κ(T) and ρ(T) relations were measured on a sample cut along the direction of tree growth. The experimental results obtained are analyzed.     

Electron temperature determination in LTE and non-LTE plasmas

A method is presented for calculating electron temperatures (T_e) in dense plasmas, which does not assume equivalence with the excited level distribution temperatures (T_ex). The method involves the upper-level Saha ionization equation at the ionization limit, the limiting weighted population density (N_I/g_I) obtained from measured population densities and the experimentally obtained electron density. Electron temperatures calculated for 0.1-bar hydrogen and 1-atm helium and argon arcs are found to be up to twice as large as excited level distribution temperatures. For subatmospheric argon arcs, the calculated T_e are equivalent to the excitation temperature of the middle levels, but are two to three times smaller than the quoted T_ex for the highest levels. Reasons are discussed for the apparent invisibility of true electron temperatures and for differences between them and the excitation temperatures.     

The influence of nickel concentration on photoluminescence spectra of ZnSe:Ni samples

Photoluminescence (PL) spectra of ZnSe samples grown by iodine transport method and doped with Ni during the growth process and grown from the melt and doped with Ni by diffusion from a gas phase are investigated in visible and infrared (IR) ranges at 77 and 300 K. It is shown that under sub-band excitation, the PL spectra for the undoped samples of both types are similar and may be attributed to self-activated luminescence with participation of iodine- and V_Zn-based centres. The PL study for ZnSe samples doped with Ni carried out at various Ni concentrations, temperatures, and excitation intensities gives reason to ascribe the observed bands in near-IR and IR ranges to ³T₂(F)→³T₁(F) and ³T₁(P)→³T₁(F) intracentre transitions within the Ni_Zn²⁺(d⁸) ion.     

Streuung von 25 keV-Elektronen an Gasen

The differential cross section of neon, argon, krypton, and xenon for the elastic scattering and for the excitation of optical transitions has been measured. For neon and argon the elastic angular distribution can be described by the cross section calculated according toWentzel andLenz. For krypton and xenon there are considerable deviations from the Wentzel-Lenz cross section. In these cases it is better to calculate the elastic differential cross section from Slater eigenfunctions, from Thomas-Fermi-Dirac or from Hartree-Fock electron density distribution. The differential cross sections for the excitation of optical transitions, so far as measured here, obey for?<? _c the dipol approximation, i.e. for angles not to small the inverse square angular dependence is valid.? _c is higher for the heavier rare gases. The oscillator strengths for some transitions have been determined from the scattering measurements in satisfactory agreement with theoretical values.     

On the Debye temperature and Grüneisen parameters for hexagonal close-packed crystals consisting of p-H2 and o-D2 molecules

The expressions for the Debye temperature Θ as well as for the first (γ = ?[?ln(Θ)/?ln(V)] _T ) and second (q = [?ln(γ)/?ln(V)] _T ) Grüneisen parameters are derived based on the Mie-Lennard-Jones pair atomic interaction potential. The conditions imposed on the Θ(V/V ₀), γ(V/V ₀), and q(V/V ₀) dependences for V/V ₀ → 0 and for V/V ₀ → ∞ are analyzed. Here, V/V ₀ is the ratio of the molar volumes for pressure P at temperature T and for P = 0 at T = 0 K. Calculations are performed for crystals of parahydrogen and orthodeuterium at T = 0 K for V/V ₀ ranging from 1.30 to 0.01. Good agreement is reached between the calculated dependences and experimental data. The behavior of dependences Θ(V/V ₀), γ(V/V ₀), and q(V/V ₀) upon a variation of the isotopic composition of the crystal is analyzed.     

Accurate second Kerr virial coefficient of rare gases from the state-of-the-art ab initio potentials and (hyper)polarizabilities

The second Kerr virial coefficient of rare gases is studied in this work using the best ab initio potentials and (hyper)polarizabilities in the literature. The second Kerr virial coefficient of helium-4, helium-3, neon, argon, and krypton and its polarizability component of xenon are computed by the semi-classical method together with the Padé approximant over a wide temperature range. In addition, the uncertainty of second Kerr virial coefficient is estimated from the uncertainties of the ab initio interaction-induced properties. The experimental and theoretical data in the literature is compared with our calculated values to examine the quality of this work. It is shown that our computed values in the supplementary materials are as accurate as the literature data at medium and high temperatures and are more reliable at low temperatures.     

Application d'un modéle de l'état liquide à une monocouche de xénon ou de krypton adsorbées sur la surface (0001) du graphite

A phenomenological model of three-dimensional (3D) liquids is applied to a xenon or krypton monolayer adsorbed on (0001) graphite. The rare-gas atoms are assumed to be mobile with a short-range order as in 3D liquids. From the study of the equilibrium 3D gas ? 2D solid and 3D gas ? 2D liquid, one can find with reasonable agreement the pressures and temperatures of the 2D triple point determined experimentally by other authors.