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We show that thermodynamic scaling can be derived by combining the Murnaghan equation of state (EOS) with the generalized entropy theory (GET) of glass formation. In our theory, thermodynamic scaling arises in the non-Arrhenius relaxation regime as a scaling property of the fluid configurational entropy density $s_c$, normalized by its value $s_c^*$ at the onset temperature $T_A$ of glass formation, $s_c / s_c^*$, so that a constant value of $TV^{\gamma}$ corresponds to a \textit{reduced isoentropic} fluid condition. Molecular dynamics simulations on a coarse-grained polymer melt are utilized to confirm that the predicted thermodynamic scaling of $\tau_{\alpha}$ by the GET holds both above and below $T_A$ and to test whether the extent $L$ of stringlike collective motion, normalized its value $L_A$ at $T_A$, also obeys thermodynamic scaling, as required for consistency with thermodynamic scaling. While the predicted thermodynamic scaling of both $\tau_{\alpha}$ and $L/ L_A$ is confirmed by simulation, we find that the isothermal compressibility $\kappa_T$ and the long wavelength limit $S(0)$ of the static structure factor do not exhibit thermodynamic scaling, an observation that would appear to eliminate some proposed models of glass formation emphasizing fluid `structure' over configurational entropy. It is found, however, that by defining a low temperature hyperuniform reference state, we may define a compressibility relative to this condition, $\delta \kappa_T$, a transformed dimensionless variable that exhibits thermodynamic scaling and which can be directly related to $s_c / s_c^*$. Further, the Murnaghan EOS allows us to interpret $\gamma$ as a measure of intrinsic anharmonicity of intermolecular interactions that may be directly determined from the pressure derivative of the material bulk modulus., Comment: 77 pages, 14 figures

The purpose of the current study is to propose a procedure to predict the effect of pressure on biodiesel density based on fatty acid alkyl ester profiles and density values at atmospheric pressure. Based on a Murnaghan equation of state to describe the effects of pressure on density and a group-contribution method to factor in the diversity of fatty acid alkyl ester components in biodiesels, the method is applicable up to 200 MPa in a wide temperature range from 280 to 400 K. Comparison of results with experimental data show that the method provides reliable high pressure predictions for biodiesels and biodiesel blends. Typical deviations calculated between the proposed method and experimental data are 0.05% for Fatty Acid Methyl Esters and 0.04% for Fatty Acid Ethyl Esters in terms of Average Absolute Deviation, with maximum deviations of the same order of magnitude as those of experimental uncertainties.

Mesoscale simulation using the material point method (MPM) was conducted to study the pressure&ndash, volume (PV) variations of Octahydro-1,3,5,7-Tetranitro-1,2,3,5-Tetrazocine (HMX)/Estane polymer-bonded explosive (PBX) under impact loading. The PV isotherms and Hugoniot data were calculated for the different porosities and binder volume fractions. The PV isotherms were used to determine the parameters for the Birch&ndash, Murnaghan equation of state (EOS) for the PBX. From the EOS, the isothermal bulk modulus (K0) and its pressure derivative () were calculated. Additionally, the pseudo particle velocity and pseudo shock velocity variations were used to obtain the bulk wave speed c and dimensionless coefficient s for the Mie&ndash, Gr&uuml, neisen EOS. The simulations provide an alternative approach for determining an EOS that is consistent with experimental observations.

The physical behavior of perovskites ATiO3 (A=Pb, Sn) has been explored by using density functional theory based full-potential linearized-augmented-plane-wave plus local-orbital (FP-LAPW+lo) method. The lattice parameters calculated from the optimized structures by using Murnaghan equation of state and Chapin's method have been found in good agreement with the available literature that ensures the reliability of the adopted methodology. Moreover, the optoelectronic and thermoelectric properties have been elaborated by using modified Becke-Johnson exchange potential. The optical behavior has been explored in terms the dielectric constants, refractive indices, absorption spectra and optical loss factors. The absorption spectra of these materials reveal a large absorption in the visible and low ultraviolet part of incident light. The thermoelectric properties of ATiO3 are explained in terms of electrical conductivities, thermal conductivities, power factors, and the specific heat capacities. The ATiO3family of pervoskites has been found to exhibit the bandgaps falling in the visible region of solar spectrum and show high values of thermal efficiency that make them potential multifunctional candidates for optoelectronic and energy harvesting applications.

The dynamic cavity expansion (DCE) model is a commonly used analytical model to predict the resistance of concrete materials subjected to projectile impact. In this paper, a modified Griffith strength criterion was proposed for reactive powder concrete (RPC), which has a form easy to solve and can well capture the tensile, compressive and triaxial strength of RPC. Combined with the Murnaghan equation of state, the proposed strength criterion was used as the material model for RPC. The cavity expansion resistance was calculated numerically and analytically. It indicates that the numerical and analytical solutions are almost consistent under the same material response. Then, the strain softening behavior that cannot be resolved analytically was further introduced into the material model, and the numerical solution of the DCE model was obtained using LS-DYNA. To verify the present method, the 122.6 MPa RPC targets were tested using 14.5 mm diameter ogival nose projectiles at impact velocities of from 286 to 942 m/s. Combined with previous penetration model, the penetration depth of the present test was predicted. In addition, numerical simulation of this penetration test adopting the HJC model was also performed. It shows predictions of the present model are in good agreement with test and simulation results. Furthermore, the present model was used to predict the existing test date of RPCs with compressive strength of between 67.5 and 140 MPa, and the effectiveness of the present method was verified by comparing with predictions of previous empirical formulas.

Journal of applied physics 127(5), 055903 - (2020). doi:10.1063/1.5135649, The p-V-T equation of state of magnesium metal has been measured up to 20 GPa and 1500 K using both multianvil and opposite anvil techniques combined with synchrotron x-ray diffraction. To fit the experimental data, the model of Anderson–Grüneisen has been used with fixed parameter δT. The 300-K bulk modulus of B0 = 32.5(1) GPa and its first pressure derivative, B0′ = 3.73(2), have been obtained by fitting available data up to 20 GPa to the Murnaghan equation of state. Thermal expansion at ambient pressure has been described using second order polynomial with coefficients a = 25(2) × 10−6 K−1 and b = 9.4(4) × 10−9 K−2. The parameter describing simultaneous pressure and temperature impact on the thermal expansion coefficient (and, therefore, volume) is δT = 1.5(5). The good agreement between fitted and experimental isobars has been achieved to relative volumes of 0.75. The Mg melting observed by x-ray diffraction and in situ electrical resistivity measurements confirms previous results and additionally confirms the p-T estimations in the vicinity of melting., Published by American Inst. of Physics, Melville, NY

A hyperbolic yield criterion and Murnaghan equation of state were introduced to describe the plastic behavior of concrete material under projectile penetration, and an extended dynamic cavity expansion model was proposed. Then, a unified one-dimensional resistance of concrete target to projectile penetration was formulated, in which the projectile nose shape influences were taken into account by three non-dimensional coefficients. Furthermore, combined with the Newton's second law and Alekseevskii-Tate equations, both rigid and eroding projectile penetration models into concrete targets were established. By comparing with the existing tests data as well as prediction results of previous model based on the linear yield criterion and equation of state, the proposed models were verified. Besides, a series of practical parameters of hyperbolic yield criterion and Murnaghan EOS for the extended dynamic cavity expansion model were given and verified.

We have investigated the influence of the Hubbard (effective) U correction parameter on the structural, local magnetic moment, electronic, mechanical and elastic anisotropy properties of SeXO3 compounds from the first-principles computations. The equilibrium volumes, total energy, bulk moduli and its pressure derivative of the four different magnetic configurations of the SeXO3 compound are assessed by the Murnaghan equation of state fittings. Comparing the ground state of total energy, we have found that the G-type antiferromagnetic configuration in SeXO3 compounds is more stable than other magnetic configurations. Electronic band structure computations indicate that both compounds exhibit a semiconductor behavior. The elastic, polycrystalline elastic and anisotropic properties of both compounds in G-type antiferromagnetic phase were investigated. With the present research, the prediction of these mechanical properties of SeXO3 compounds will guide the elastic constant measurements of these compounds in the future.

In situ high-pressure X-ray diffraction experiments and reverse Monte Carlo simulations on Pd81Si19 glassy alloy were performed up to similar to 35 GPa. High-quality structure factor data with a q range up to 13.5 angstrom(-1) were obtained. The pressure dependence of the relative volume of Pd81Si19 glassy alloy can be well described by a third-order Birch Murnaghan equation of state with bulk modulus of B-0 = 229 GPa and a pressure derivative of B-0(') = 2.7. The continuous and monotonic change of relative volume as a function of pressure does not indicate any first-order phase transitions in Pd81Si19 glassy alloy in the studied pressure range. The pressure dependence of the atomic structures was systematically investigated by means of bond angle distribution, the Honeycutt and Andersen index, Voronoi tessellation, total and partial coordination numbers, and local chemical ordering analyses. It is found that the topological and chemical atomic structures of the Pd81Si19 glassy alloy do not change much with pressure, indicating the stability of this material under pressure. (C) 2014 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.

The high-pressure elastic properties behavior, phase stability, and mechanisms of amorphization of the alumino-silicate 7:4 mullite and a corresponding mullite doped with boron were investigated in situ by powder synchrotron X-ray diffraction with a diamond anvil cell in quasi-hydrostatic conditions. The samples of 7Al2O3:4SiO2 (Al4.66Si1.33O9.67), referred to as 7:4 mullite and an alumino-silicate mullite with 3.5(4) mol% B2O3, referred to as B-mullite, were compressed, in small pressure steps, up to 27.8 and 28.9 GPa, respectively, and then decompressed back to ambient pressure. All along the compression path both samples' patterns are indexable with a mullite structure. Compression data are smooth up to a threshold pressure, from which point the diffraction peaks appeared to broaden, and the refined unit cell parameters deviate significantly down from the compressional trend. Above ~23 GPa the diffraction patterns are not indexable anymore, suggesting amorphization. Rietveld structural refinements allow for a description of the pressure-induced main deformation mechanisms and structural trends. Pressure-induced mechanisms of amorphization are also discussed. A third-order Birch Murnaghan equation of state is fitted to the pressure-volume data to obtain experimental bulk moduli, as well as axial compressibilities for 7:4 mullite and B-mullite. Finally the volume compression in response to the applied pressure, combined with thermal expansion coefficients, allows a P–T–V equation-of-state for B-mullite to be proposed.

In order to examine the potential of using the coupled smooth particles hydrodynamic (SPH) and finite element (FE) method to predict the dynamic responses of aircraft structures in bird strike events, bird-strike tests on the sidewall structure of an aircraft nose are carried out and numerically simulated. The bird is modeled with SPH and described by the Murnaghan equation of state, while the structure is modeled with finite elements. A coupled SPH–FE method is developed to simulate the bird-strike tests and a numerical model is established using a commercial software PAM-CRASH. The bird model shows no signs of instability and correctly modeled the break-up of the bird into particles. Finally the dynamic response such as strains in the skin is simulated and compared with test results, and the simulated deformation and fracture process of the sidewall structure is compared with images recorded by a high speed camera. Good agreement between the simulation results and test data indicates that the coupled SPH–FE method can provide a very powerful tool in predicting the dynamic responses of aircraft structures in events of bird strike.

Hydrogen is one of the most promising energy sources of the future enabling direct production of power and heat in fuel cells, hydrogen engines or furnaces with hydrogen burners. One of the last remainder problems in hydrogen technology is how to produce a sufficient amount of cheap hydrogen. One of the best options is large scale thermochemical production of hydrogen in combination with nuclear power plant. copper-chlorine (CuCl) cycle is the most promissible thermochemical cycle to produce cheap hydrogen.This paper focuses on a CuCl cycle, and the describes the models how to calculate thermodynamic properties. Unfortunately, for many components in CuCl cycle the thermochemical functions of state have never been measured. This is the reason that we have tried to calculate some very important thermophysical properties. This paper discusses the mathematical model for computing the thermodynamic properties for pure substances and their mixtures such as CuCl, HCl, Cu2OCl2 important in CuCl hydrogen production in their fluid and solid phase with an aid of statistical thermodynamics. For the solid phase, we have developed the mathematical model for the calculation of thermodynamic properties for polyatomic crystals. In this way, we have used Debye functions and Einstein function for acoustical modes and optical modes of vibrations to take into account vibration of atoms. The influence of intermolecular energy we have solved on the basis of Murnaghan equation of state and statistical thermodynamics.

An ab initio study of structural, electronic, elastic, and dielectric properties of KMgF3 in cubic perovskite structure is presented in the framework of density functional theory. The calculations presented here employ generalized gradient approximation with projector augmented wave method. The fully relaxed structural parameters are found to be in reasonable agreement with available experimental data and with previous theoretical work. The independent elastic constants of cubic KMgF3 are derived from the derivative of total energy as a function of lattice strain in full detail. The bulk modulus and its first pressure derivative are obtained by fitting total energy versus volume data to a Murnaghan equation of state. The electronic band structure, total density of states, and projected density of states on each of the K, Mg, and F atoms are calculated and found to be in good agreement with previous theoretical results. First principles computed phonon dispersions for the cubic KMgF3 are reported for the first time. The imaginary part of frequency-dependent dielectric function is determined by summing over all possible transitions from occupied to unoccupied states and taking the appropriate transition matrix element into account. The Born effective charges computed by linear response within density functional perturbation theory are used together with the mode eigenvectors to decompose the lattice dielectric susceptibility tensor into contributions arising from individual IR-active phonon modes. Our results for the static and optical dielectric constant are in good agreement with previously reported experimental results.

Recent satellite inferences of hydrous sulfates as recurrent minerals on the surface of icy planetary bodies link with the potential mineral composition of their interior. Blodite, a mixed Mg-Na sulfate, is here taken as representative mineral of icy satellites surface to investigate its crystal structure and stability at conditions of the interior of icy bodies. To this aim we performed in situ synchrotron angle-dispersive X-ray powder diffraction experiments on natural blodite at pressures up to ∼10.4 GPa and temperatures from ∼118.8 K to ∼490.0 K using diamond anvil cell technique to investigate the compression behavior and establish a low-to-high temperature equation of state that can be used as reference when modeling the interior of sulfate-rich icy satellites such as Ganymede. The experimentally determined volume expansivity, α, varies from 7.6 (7) 10−5 K−1 at 0.0001 GPa (from 118.8 to 413.15 K) to 2.6 (3) 10−5 K−1 at 10 GPa (from 313.0 to 453.0 K) with a δα/δP coefficient = −5.6(9)10−6 GPa−1 K−1. The bulk modulus calculated from the least squares fitting of P-V data on the isotherm at 413 K using a second-order Birch - Murnaghan equation of state is 38(5) GPa, which gives the value of δK/δT equal to 0.01(5) GPa K−1. The thermo-baric behavior of blodite appears strongly anisotropic with c lattice parameter being more deformed with respect to a and b. Thermogravimetric analyses performed at ambient pressure showed three endotherms at 413 K, 533 K and 973 K with weight losses of approximately 11%, 11% and 43% caused by partial dehydration, full dehydration and sulfate decomposition respectively. Interestingly, no clear evidence of dehydration was observed up to ∼453 K and ∼10.4 GPa, suggesting that pressure acts to stabilize the crystalline structure of blodite. The data collected allow to write the following equation of state, V(P, T) = V0[1 + 7.6(7)10 − 5ΔT − 0.026(3)P − 5.6(9)10 − 6PΔT−6.6(9)10 − 6PΔT)] from which the density of blodite can be determined at conditions of the mantle of the large icy satellites of Jupiter. Blodite has higher density, bulk modulus and thermal stability than similar hydrous sulfates (e.g. mirabilite and epsomite) implying, therefore, a different contribution of these minerals to the extent of deep oceans in icy planets and their distribution over the local geotherms.

New boron subnitride B50N2 has been synthesized by crystallization from the B–BN melt at 5 GPa, and its structure has been refined using Rietveld analysis. B50N2 crystallizes in the tetragonal space group P-4n2 with unit cell parameters a0 = 8.8181(2) A and c0 = 5.0427(10) A. Quasi-hydrostatic compression of two boron subnitrides, B50N2 and B13N2, has been studied up to 30 GPa at room temperature in a diamond-anvil cell using synchrotron X-ray diffraction. No pressure-induced phase transitions have been observed. A fit of experimental p-V data to the Murnaghan equation of state yielded B50N2 and B13N2 bulk moduli of 167(2) and 205(2) GPa, respectively, with fixed first bulk modulus pressure derivative of 4.0.

One of the fundamental physical quantities necessary to describe the mechanical properties of the materials is the bulk modulus. In the present report, a simple method to estimate the values of the bulk modulus and its pressure derivative of metallic glasses is presented. The method which is based on a jellium model of metals provides a good agreement with measured data. The estimated values of the elastic constants have been used to determine the equation of state of bulk metallic glasses. It is found that the usual Murnaghan equation of state deviates considerably from the experimental results at high pressures. The deviation has been interpreted to arise from the structural relaxations. The effect of pressure on the fragility of bulk metallic glasses is discussed briefly.

The effect of Ni-substitution on magnetic properties of Ni2MnGe alloy has been investigated by first principles method FPLO, which is used in the CPA form. The theoretical lattice parameters obtained from the dependence of the total energy on the lattice parameter are comparable with experimental ones. A decreasing trend of total magnetic moment with Ni-substitution is found for Ni2+xMn1−xGe for studied concentrations of x. The linear pressure-magnetization behaviour is obtained for Ni2+xMn1−xGe for applied pressure from 0 to 9 GPa, and the pressure derivative of the total magnetic moment is calculated. The value of equilibrium bulk modulus of Ni2+xMn1−xGe (for x = 0.1 – 0.9) obtained from Murnaghan equation of state (EOS) shows that the studied compounds are less compressible than Ni2MnGe.

The optimized crystal structures, band structures, partial and total densities of states (DOS), dielectric functions, refractive indexes and elastic constants for ZnAl 2 S 4 and ZnGa 2 O 4 were calculated using the CASTEP module of Materials Studio package. Pressure effects were modeled by performing these calculations for different values of external hydrostatic pressure up to 50 GPa. Obtained dependencies of the unit cell volume on pressure were fitted by the Murnaghan equation of state, and the relative changes of different chemical bond lengths were approximated by quadratic functions of pressure. Variations of applied pressure were shown to produce considerable re-distribution of the electron densities around ions in both crystals, which is evidenced in different trends for the effective Mulliken charges of the constituting ions and changes of contour plots of the charge densities. The longitudinal and transverse sound velocities and Debye temperatures for both compounds were also estimated using the calculated elastic constants.

The high-pressure behavior of TlTeVO5 has been investigated in situ using single-crystal X-ray diffraction in a diamond anvil cell. This material is structurally stable at least to 7.11 GPa, the highest pressure reached in this study. TlTeVO5 is twinned both at ambient and high pressures (Pna21, Z=4). The twinning law relating the two individuals is equivalent to a rotation of approximately 3° around the [ 1 2 ¯ 0 ] direction. Within errors, no changes in the orientation of the two individuals are observed as a function of pressure. The refined twin volume fractions do not change within estimated standard deviations, either. The material is the most and the least compressible along the c and a axes, respectively. The P–V data could be fitted by a Murnaghan equation of state with B0=32(1) GPa, V0=504.4(4) A3, and B′=7.97(43). The most important effect of pressure is the increase of the coordination numbers for the Tl and Te atoms. The Tl–O distance nearly parallel to the [ 001 ] direction is the most sensitive structural feature to pressure, resulting in the anisotropic compressibility. The long Te–O distances decrease, while the short ones are constant or even become slightly longer. Such a pressure-induced change of the coordination is interpreted as due to increasing uniformity of the oxygen atoms surrounding the cations and to decreasing activity of the electron lone pairs. The change is accompanied by an increase of the pseudosymmetry of the structure with respect to the centrosymmetric space group Pnna.

We evaluated the thermal stability and isothermal bulk modulus of the cubic (c), tetragonal (t), and monoclinic (m) ZrO2 polymorphs at room temperature by molecular dynamics with a semi-empirical quantum-chemical model. The procedure used was based on the semi-empirical calculation of the lattice energy of the different polymorphs as a function of the lattice volume, followed by fitting the Murnaghan equation of state to these lattice energy–volume curves. This yields directly the equilibrium lattice energy (E0), the equilibrium lattice volume (V0), and the bulk modulus (B0). The monoclinic form ( E 0 m = − 119.41 eV / Zr O 2 ) was found to be more stable than the tetragonal form ( E 0 t = − 119.29 eV / Zr O 2 ), which in turn was more stable than the cubic form ( E 0 c = − 119.21 eV / Zr O 2 ). We thence deduced the existence of the cubic–monoclinic and tetragonal–monoclinic phase transformations, and calculated the volume changes associated with these phase transformations (∼3.9–4.5%) from V 0 c , V 0 t , and V 0 m . Also, we found that the bulk moduli of the ZrO2 polymorphs are close to 200 GPa, and are in the sequence B 0 t > B 0 c > B 0 m . All these results were in clear agreement with the literature data, obtained by complex ab initio molecular dynamics and/or sophisticated experimental techniques. This suggests that applications of molecular dynamics with semi-empirical quantum-chemical models may have an important role to play in the theoretical design of ceramic materials.

The effect of pressure on the Fe 3+ /∑Fe ratio of an anhydrous andesitic melt was determined from 0.4 to 3.0 GPa at 1400 °C with oxygen fugacity controlled internally by the Ru + RuO 2 buffer. Values of Fe 3+ /∑Fe were determined by Mossbauer spectroscopy on quenched glasses with a precision of ±0.01, one standard deviation. This precision was verified independently by XANES spectroscopy of the same samples. The XANES spectra show a systematic increase in energy and decrease in intensity of the 1s → 3d transition with increasing pressure. The results to 2.0 GPa are in good agreement with predictions from density and compressibility measurements fitted to a Murnaghan equation of state, but the datum at 3.0 GPa has higher Fe 3+ /∑Fe than predicted from the trend established by the lower-pressure data. This might be due to a coordination change in Fe 3+ at high pressure; although there is no evidence for this in the Mossbauer spectra, such a change could account for the change in intensity of the 1s → 3d transition in the XANES spectra with pressure.

Unit-cell parameters of zoisite, Ca 2Al3Si3O12(OH), have been measured at simultaneously high pressures and temperatures (up to 6.1 GPa and 800 8C) in a Walker-style multi-anvil apparatus at the synchrotron radiation source at Daresbury Laboratory, U.K. Measurements were made in a series of heating cycles at increasing loads. Sample pressure, measured using an internal NaCl standard, increased during heating. Cell parameters vary smoothly with pressure and temperature; individual expansivities and compressibilities vary in the order c . b . a. Isothermal bulk moduli were calculated from the volumes measured at 30, 200, 400, 600, and 800 8C by fitting the Murnaghan equation of state to each isothermal data set. This assumes K 95 4. Ambient-pressure volumes calculated from previous measurements of thermal expansivity of zoisite were included in the Murnaghan fits. A linear fit of the bulk moduli with temperature gave values for the bulk modulus at 298 K, K298 5 125(3) GPa, and its variation with temperature, ]KT/]T 52 0.029(6) GPa K 21 . K298 is slightly higher than the recent value for a single crystal in a diamond-anvil cell, indicating a lower maximum pressure stability of zoisite than would be calculated using that value. Our data allow zoisite volumes to be calculated at P-T conditions relevant to the Earth and show that, in a typical subduction zone, zoisite becomes more dense as subduction proceeds, helping to stabilize it to high pressures.

The heat capacity of synthetic, stoichiometric wadeite-type K2Si4O9 has been measured by DSC in the 195≤T(K)≤598 range. Near the upper temperature limit of our data, the heat capacity observed by DSC agrees with that reported by Geisinger et al. (1987) based on a vibrational model of their infrared and Raman spectroscopic data. However, with decreasing temperature, the Cp observed by DSC is progressively higher than that predicted from the vibrational model, suggesting that the standard entropy of K2Si4O9 is likely to be larger than 198.9 ± 4.0 J/K · mol computed from the spectroscopic data. A fit to the DSC data gave: Cp(T) = 499.13 (±1.87) − 4.35014 · 103(±3.489 · 101) · T −0.5, with T in K and average absolute percent deviation of 0.37%. The room-temperature compressibilities of kalsilite and leucite, hitherto unknown, have been measured as well. The data, fitted to the Murnaghan equation of state, gave K o = 58.6 GPa, K o ′ = 0.1 for kalsilite and K o = 45 GPa, K o ′ = 5.7 for α-leucite. Apart from the above mentioned data on the properties of the individual phases, we have also obtained reaction-reversals on four equilibria in the system K2O-Al2O3-SiO2. The Bayesian method has been used simultaneously to process the properties of 13 phases and 15 reactions between them to derive an internally consistent thermodynamic dataset for the K2O-Al2O3-SiO2 ternary. The enthalpy of formation of K2Si4O9 wadeite is in perfect agreement with its revised calorimetric value, the standard entropy is 232.1 ± 10.4 J/K · mol, ∼15% higher than that implied by vibrational modeling. The phase diagram, generated from our internally consistent thermodynamic dataset, shows that for all probable P-T trajectories in the subduction regime, the stable pressure-induced decomposition of K-feldspar will produce coesite + kalsilite rather than coesite + kyanite + K2Si4O9 (cf. Urakawa et al. 1994).

The pressure dependence of the lattice parameters of natural zoisite [Ca2A13Si3012(OH)], clinozoisite [Ca2A13Si30'2(OH)], and epidote [Ca2A12FeSi3012(OH)] as well as synthetic lawsonite [CaAl2Si207(OH)2' H20] have been measured at ambient temperatures by energy-dispersive X-ray diffraction in a diamond-anvil cell. The experimental results for each phase may be summarized concisely in terms ofthe ambient-temperature isothermal bulk modulus K298(using the Murnaghan equation of state and assuming K' = 4): Lawsonite: K298= 191 :t 5 GPa; zoisite: K298= 279 :t 9 GPa; clinozoisite: K298= 154 :t 6 GPa; epidote: K298= 162 :t4 GPa. These new measurements, together with the new thermal expansion data in the companion paper (Pawley et al. 1996), were used to calculate some phase equilibria for lawsonite dehydration to high pressures for comparison with experimental brackets. Important discrepancies between calculated and experimentally determined reactions become evident above 3 GPa.

The study of the effects of applying high pressure by compression on materials is fundamental to a range of problems in condensed matter physics, materials science, technology, etc. Transition of an insulator into a metallic state is in general a basic phenomenon related to a wide range of physical systems. Nickel monoxide has been studied at different volume compression ratios by employing optical spectra and electronic structure calculations using the density functional theory implemented in the MindLab 5 code that made use of the local density approximation plus the Hubbard on-site Coulomb interaction parameter. Insulator-metal transition point was recorded at 0.60 volume compression ratio from both calculations and a transition pressure of 271 GPa was obtained using the Murnaghan equation of state.

The high pressure behaviour of 3R-NbS2 has been investigated by angle-dispersive X-ray powder diffraction using diamond anvil cells up to 14 GPa. The compression behaviour of the structure is highly anisotropic. The compressibility perpendicular to the layers is 2.5 times higher than within the layers. A fit of a 3 rd -order Birch-Murnaghan equation of state gave a volume at zero pressure V 0=174(1) Å3 and a bulk modulus b 0=57(1) GPa, with a pressure derivative b'=8.6(5).

The compressibilities of reedmergnerite (NaBSi 3 O 8 ) and danburite (CaB 2 Si 2 O 8 ) have been determined between 0 GPa and 5 GPa by single crystal X-ray diffraction, using a Merrill-Bassett diamond anvil cell. Further compressibility studies on anorthite (CaAl 2 Si 2 O 8 ) between 0 GPa and 2.55 GPa and the use of previously published data for albite (NaAlSi 3 O 8 ) enabled the Murnaghan equation of state to be fitted to the volume, pressure data and a bulk modulus obtained for each crystal structure. For a straight comparison of unit cell volume changes with pressure it was necessary to fix K' at 4. For sections involving the change of bulk modulus with increasing Al/Si disorder K' was fixed at four separate values to confirm that the trends observed were real. Comparison of changes in unit cell volume with pressure allows a number of conclusions to be made : The extra framework cation M″ plays a major role in determining structure compressibility, substitution of B for Al results in a increase in bulk modulus, and increasing Al/Si disorder leads to a decrease in the bulk modulus of the anorthite structure. The comparison of strain ellipsoids for reedmergnerite and albite confirm that the major structural changes with increasing pressure are driven by changes in T-O-T bond angles

The influence of external pressure, up to 30 GPa, on the structural properties of MnAs 0.88 P 0.12 has been studied for temperatures between 300 and 450 K by energy dispersive X-ray diffraction using synchrotron radiation. MnAs 0.88 P 0.12 undergoes a very large, continuous volume contraction when subjected to pressure. The experimental pV relationship is discussed on the basis of the first-order Birch and Murnaghan equations of state, and the structural changes are discussed in relation to similar observations for isostructural (MnP-type) phases. The experimental results at 300, 350, and 450 K are in excellent agreement with earlier estimations of the temperature dependence of the compressibility which were based on the chemical pressure concept with starting point in the equivalency of the p , T phase diagram of MnAs and the x , T phase diagram of MnAs 1− x P x . The isothermal bulk modulus B 0 and its pressure derivative B ′ 0 are, according to the Murnaghan equation of state, respectively 18 GPa and 10 at 300 and 450 K and respectively 10 GPa and 18 at 350 K. Values for the Gibbs energy and the entropy as 300 K are tabulated as functions of applied pressure.

The structural and electronic properties of crystalline pentacene has been investigated within the framework of density functional theory including van der Waals interactions. The computed lattice parameters have good agreement with experimental data. We studied on the structural and electronic properties of the pentacene under the hydrostatic pressure of 0-10 GPa. The isothermal equations of state calculated from the results show good agreement with experiment in the pressure intervals studied. Using the Murnaghan equation of state it has been established that compression bulk modulus is B0=11.42 GPa and it has good agreement with the experimental value. We have also calculated the quasiparticle band structure of pentacene with the G0W0 approximation.

The compressibilities of ethylenglycol and ethanolamin silica sodalite (EGS-SOD and EAS-SOD) have been measured up to 3. 1 and 3. 2 GPa, respectively. Both compounds show extraordinarily high compressibilities, from a fit to a Birch Murnaghan equation of state the bulk moduli and pressure derivatives calculate to K=8. 3 (5) GPa, K'=8 (1) and K=9. 7 (7) GPa, K'=3. 8 (7). EGS-SOD shows three phase transitions to a monoclinic and two triclinic high pressure phases in the pressure range investigated. These phase transitions are completely reversible and no twinning has been observed while passing the transition pressures. The structures of the monoclinic and of the 1st triclinic high pressure phase have been solved on the basis of intensity data collected with synchrotron radiation. Whereas the ethylenglycol guest molecules are dynamically disordered under room conditions, they adopt an ordered arrangement in the 2nd high pressure phase. Structure refmements of EASSOD again reveal a triclinic high pressure phase at 1. 1 GPa.

Uranium manganese germanide, UMn2Ge2, crystallizes in body-centered tetragonal ThCr2Si2 structure with space group I4/mmm, a=3.993 A and c=10.809 A under ambient conditions. Energy dispersive X-ray diffraction was used to study the compression behavior of UMn2Ge2 in a diamond anvil cell. The sample was studied up to static pressure of 26 GPa and a reversible structural phase transition was observed at a pressure of 1 6.1 GPa . Unit cell parameters were determined up to 12.4 GPa and the calculated cell volumes were found to be well reproduced by a Murnaghan equation of state with K 0 =73.5 GPa and K′=11.4. The structure of the high-pressure phase above 16.0 GPa is quite complicated with very broad lines and could not be unambiguously determined with the available instrument resolution.

In this paper, structural and electronic properties of L12 and D019- AlSc 3 are presented. Calculations are performed applying crystalline orbital program within the framework of density functional theory. The exchange and correlation are treated following the Perdew–Becke–Ernzerhof ansatz. Other Al – Sc intermetallic compounds and polymorphs of Al 3 Sc , Al 2 Sc and AlSc are also investigated. The total energy calculations are coupled with the Murnaghan equation of state to determine lattice constants and bulk moduli. The data for D019- AlSc 3 are provided while deduced structural parameters for other materials are compared with the available results. Current results are reasonably in agreement with the experimental data and other reported calculations. Electronic band structures of a few Al – Sc compounds are studied with a view to examine effect of Al concentration on the formation of bands and bonds in the Al – Sc system.

Group Theoretical Methods as defined by Lie are applied to the problem of temperature independent, hydrodynamic shock in a Birch-Murnaghan continuum. Ratios of the group parameters are shown to be linked to physical parameters specified in the second, third, and fourth order BM-EOS approximations. We provide an illustrative example of how the expansion ratio (c1/c2) and the material resistance condition (c4/c2) are a function of the compression ratio β, for a spherical shock wave propagating through MgO and Na.

The high-pressure behavior of KIO(3) was studied up to 30 GPa using single crystal and powder x-ray diffraction, Raman spectroscopy, second harmonic generation (SHG) experiments and density functional theory (DFT)-based calculations. Triclinic KIO(3) shows two pressure-induced structural phase transitions at 7 GPa and at 14 GPa. Single crystal x-ray diffraction at 8.7(1) GPa was employed to solve the structure of the first high-pressure phase (space group R3, a = 5.89(1) Å, α = 62.4(1)°). The bulk modulus, B, of this phase was obtained by fitting a second order Birch-Murnaghan equation of state (eos) to synchrotron x-ray powder diffraction data resulting in B(exp,second) = 67(3) GPa. The DFT model gave B(DFT,second) = 70.9 GPa, and, for a third order Birch-Murnaghan eos, B(DFT,third) = 67.9 GPa with a pressure derivative of [Formula: see text]. Both high-pressure transformations were detectable by Raman spectroscopy and the observation of second harmonic signals. The presence of strong SHG signals shows that all high-pressure phases are acentric. By using different pressure media, we showed that the transition pressures are very strongly influenced by shear stresses. Earlier work on low- and high-temperature transitions was complemented by low-temperature heat capacity measurements. We found no evidence for the presence of an orientational glass, in contrast to earlier dielectric studies, but consistent with earlier low-temperature diffraction studies.

In situ high-pressure (up to 44-53 GPa) energy dispersive x-ray diffraction experiments have been carried out on CaTiO CaTiO 3, structure, high pressure, equation of state in a diamond anvil cell at room temperature by using synchrotron radiation. Experimental data show that the a and b axes have similar compressibilities with large variation, while the c axis is less compressible with increasing pressure. However, there is no evidence of any structural transformation in this pressure range. The isothermal P-V equation of the state of CaTiO CaTiO 3, structure, high pressure, equation of state is fitted using the Murnaghan equation of state, which yields values of V0=0.2245(6)nm 3 and K 0=222(9) GPa assuming the pressure derivative K′0=4 According to the relation of the pseudo-cubic angle γpc and pressure, the structure of CaTiO CaTiO 3, structure, high pressure, equation of state will reduce its symmetry under hydrostatic pressure.

Measurements of the effect of hydrostatic pressure on ultrasonic wave velocities have been used to determine the pressure derivatives of the elastic stiffness of uranium nitride at room temperature.∂C44/∂P, and hence the Gruneisen parameter for the transverse mode propagating down an 〈001〉 axis, is negative; however, this mode softening is not anomalous for rocksalt structure crystals. The Gruneisen gammas of the acoustic modes obtained in the long wavelength limit have a pronounced anisotropy which accrues largely from the presence or absence of contributions to modes of vibration from nearest-neighbour repulsive forces. The compression of uranium nitride calculated from the Murnaghan equation of state is much smaller than those of the alkali halides or IV–VI compounds because this compound is much stiffer.

Summary Currently available shock-wave compression data for single-crystal α-quartz and pore-free quartzite have been used to determine values for the isentropic bulk modulus of stishovite and its first pressure derivative. The shock-wave data reduction scheme makes use of the observed linearity in the shock-velocity-particle-velocity field over the pressure range 0.4–2.0 Mbar and the first-order Murnaghan equation of state. In addition, an accurate form of the temperature independent Gruneisen parameter (γ), consistent with the linear Us–up relation, has been used in the reduction of the fundamental shock-wave data to the metastable Hugoniot. The temperature derivative of the isentropic bulk modulus is provided by a least-square fit of the γ relation to available Hugoniot data directly measured on porous and fused-quartz samples in the high-pressure regime. The pertinent results are: KS= 3.35±0.19 Mbar; (∂KS/∂P)T= 5.5±0.6; and (∂KS/∂T)p= (−0.35±0.08)× 10−3 Mbar/°K. These results are consistent with recent static-compression and ultrasonic measurements on stishovite and are related systematically to corresponding data for isostructural GeO2 and TiO2. Comparison of the present results with recent shock-wave analyses by other investigators suggests that the first-order Murnaghan form of the equation of state is more appropriate than the first-order Birch equation in reproducing the compression of stishovite in the zero to 2 Mbar pressure range. An evaluation of the composition of the lower mantle in terms of the fundamental oxides, FeO, MgO, and SiO2, using the present results for the elastic properties of stishovite, support marginally the conclusions of previous investigators regarding enrichment of FeO and SiO2 relative to the upper mantle; however, such an interpretation is predicated on the mixed oxide assumption and should be considered in relation to alternative models.

The effect of pressure on the lattice constants and therefore the volume of synthetic forsterite was determined by energy-dispersive X-ray diffraction from polycrystalline material using synchroton radiation from the storage-ring DORIS at the HASYLAB, DESY (Hamburg). Pressures up to 300 kbar were applied with a diamond-anvil cell. The pressures were calculated from the volume compression by internal standard method using MgO, Fe and NaCl as pressure calibrants. The isothermal bulk modulus K0 and also its first pressure derivative K0′ (at 25°C) of forsterite have both been obtained from the experimental data with the Murnaghan equation of state by a two parameter fit yielding K0 = 1357(10) kbar and K0′=3.98(10) (standard deviations in parentheses). We found no differences with the different marker.