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Evaluation of vertical stress distribution in clay-loam soil using Smoothed-Particle Hydrodynamics-Finite Element Analysis (SPH-FEA) technique is presented in this research. The moist soil is modelled using the hydrodynamic elastic–plastic material and Murnaghan equation of state, while the tire is modelled using FEA in Visual Environment’s Pam-Crash software. Soil-tire interaction is performed using the node symmetric node to segment with edge treatment method. A single-wheel tester in a soil bin environment was utilized to provide experimental data. The objectives of the experimental test were to (1) calculate maximum subsoil stresses in the subsoil at 1 to 15 passes of a wheel with loads of 1, 2, 4, and 5 kN on soil with moisture levels of 0, 10, 17, and 24%.; (2) calibrate soil with different levels of moisture (3) compare predicted soil stresses with experiments. The maximum stress at 20 cm depth increased with increasing soil moisture and also with high levels of tire load. In contrast, successive traffic showed a decreasing effect on soil stress. The coefficient of determination 0.97 shows the predictions agreed very well with experiments. The moist soil-tire interaction model will be further used to analyze the soil stress in different soil depths and different forward velocity.

This paper focuses on predicting and analyzing the tire-moist terrain interaction. The moist terrain (sand) is modelled using Smoothed-Particle Hydrodynamics (SPH) technique. The SPH basic interpolation technique is described, and the necessary interpolation equations are implemented. The soil is modelled using the hydrodynamic elastic-plastic material, while the water is modelled using Murnaghan equation of state. The numerical interaction between both materials is defined using Darcy’s law. The soil moisturizing technique consists of layering water particles on top of sand particles and pressurizing the water into the sand. The moisturizing technique is examined using the direct shear-strength test, and validated against physical measurement carried out in a laboratory under similar soil conditions and bulk density. Finally, the results and the effect of moisture content on tire-moist terrain interaction are discussed and investigated using a previously modelled and validated off-road truck tire size 315/80R22.5.

We performed in-situ X-ray diffraction measurements of polycrystalline cubic silicon nitride samples at high temperatures under atmospheric pressure and at simultaneous high-pressure-temperature conditions. In air, cubic silicon nitride survives metastably up to 1733 K without oxidation. The temperature dependence of the thermal expansion coefficient was determined to be α(T) = a1 + a2T – a3T−2 where a1 = 1.34(6) × 10−5 K−1, a2 = 5.06(44) × 10−9 K−2, and a3 = 0.20(10) K. Using all the experimental data obtained under atmospheric and high pressures, a complete set of parameters of the high-temperature third-order Birch Murnaghan equation of state was obtained: K300,0 = 303(5) GPa, K′300,0 = 5.1(8), and (∂KT,0/∂T)P = –0.017(1) GPa K−1, where K0, K′0, and (∂KT,0/∂T)P are the isothermal bulk modulus, its pressure derivative, and its temperature derivative, respectively. These parameters are necessary to calculate the equilibrium phase boundary between the β and cubic phases in silicon nitride.

We present a first-principles study of the elastic and thermodynamic properties of the zinc-blend (ZB) InNxP1-x ternary alloy in the full range of 0 ≤ x ≤ 1. Calculations were carried out using WIEN2k code based on a non-relativistic full potential linearized augmented plan wave (FP-LAPW) method within the density functional theory (DFT). The approximation of exchange-correlation energy was performed with Generalized Gradient Approximation (GGA). The elastic constants and related mechanical properties were investigated. We have found that the stiffness coefficients increase with the increase of nitrogen content. The values of the bulk modulus derived from elastic stiffness coefficients are found to be very close to the values derived directly from Murnaghan equation of state, indicating the good accuracy of the Cij coefficients. The elastic properties were also calculated under hydrostatic pressure for (P = 0.00, 5.00, 10.0, 15.0, 20.0, 25.0 GPa). Furthermore, we have performed a quasi-harmonic Debye model calculation using GIBBS2 package to predict the thermodynamic properties and their dependences on the temperature and pressure. Thermodynamic parameters such as the Gibbs free energy, entropy, heat capacity and Debye temperature have been investigated. Our results show a good agreement with available theoretical and experimental data.

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.

An analytical model is developed to predict shockwave propagation and attenuation in hydrogels by combining the classical method of shock characteristics and a solution for the shock front structure. To guide the development of the model, molecular dynamics (MD) simulations are performed. Specifically, a one-dimensional shock pulse in poly(ethylene glycol) diacrylate (PEGDA) hydrogels is simulated with the nonequilibrium MD method. The role of polymer concentration on the shock response is evaluated by constructing hydrogels with 20, 35, and 50 wt% PEGDA concentrations in an idealized crosslinked network. Steady-state pressure-density and shock-particle velocity relationships are established using the Murnaghan equation of state. Shock front structure is characterized by a power-law equation that relates the shock front thickness with shock pressure. These results are used as critical input for the shock propagation and attenuation model. The model is then evaluated via comparison with the classical method of characteristics. It shows significant improvement in accuracy and successfully captures salient features of shockwave attenuation, including the shock pressure amplitude, the velocities of the shock and release waves, and the attenuation timeline. Hydrogels with higher polymer concentrations exhibit a shorter attenuation time at all particle velocities studied. This behavior is attributed to differences in bulk properties and shock front structure in hydrogels with different polymer/water concentrations.

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.

Theoretical calculations are performed to investigate the electronic, structural and optical properties of double perovskite oxide A2ZnTeO6 (A = Ca, Sr, Ba). The calculations are based on the Density Functional Theory (DFT) using the WIEN2k code. The exchange–correlation potential is treated with generalized gradient approximation (GGA-PBE). Additionally, the Tran Blaha modified Becke-Johnson exchange potential (TB-mBJ) is employed for electronic and optical calculations due to that it gives very accurate results of band gap in solids. In order to estimate the ground state parameters, total energies are calculated with respect to cell volume. Also, the energies are fitted with Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations reveal that these compounds exhibit semiconducting behavior with a direct band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated and discussed.

We report band structural calculations on half-Heusler alloy CoTiSi using Korringa–Kohn–Rostoker method applied for various formalism of potential. Murnaghan equation of state is used to minimize ground state total energy and then equilibrium lattice parameter is estimated. From density of state (DOS), it is seen that the Fermi energy is not lying in the gap and a close inspection of DOSs at the Fermi level reveals the absence of gap around the Fermi level suggesting the absence of half-metallic nature and the same is also confirmed by electronic band structure diagram.

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 ramp wave compression experiments of iron with different thicknesses were performed on the magnetically driven ramp loading device CQ-4. Numerical simulations of this process were done with Hayes multi-phase equation of state (H-MEOS) and dynamic equations of phase transition. The calculated results of H-MEOS are in good agreement with those of shock phase transition, but are different from those under ramp wave compression. The reason for this is that the bulk modulus of the material in the Hayes model and the wave velocity are considered constant. Shock compression is a jump from the initial state to the final state, and the sound speed is related to the slope of the Rayleigh line. However, ramp compression is a continuous process, and the bulk modulus is no longer a constant but a function of pressure and temperature. Based on Murnaghan equation of state, the first-order correction of the bulk modulus on pressure in the Hayes model was carried out. The numerical results of the corrected H-MEOS agree well with those of pure iron in both ramp and shock compression phase transition experiments. The calculated results show that the relaxation time of iron is about 30 ns and the phase transition pressure is about 13 GPa. There are obvious differences between the isentropic and adiabatic process in terms of pressure–specific volume and temperature–pressure. The fluctuation of the sound speed after 13 GPa is caused by the phase transition.

A simplified approximate model considering rod/target material’s compressibility is proposed for hypervelocity penetration. We study the effect of shockwaves on hypervelocity penetration whenever the compressibility of the rod is much larger, analogously, and much less than that of the target, respectively. The results show that the effect of shockwaves is insignificant up to 12 km/s, so the shockwave is neglected in the present approximate model. The Murnaghan equation of state is adopted to simulate the material behaviors in penetration and its validity is proved. The approximate model is finally reduced to an equation depending only on the penetration velocity and a simple approximate solution is achieved. The solution of the approximate model is in agreement with the result of the complete compressible model. In addition, the effect of shockwaves on hypervelocity penetration is shown to weaken material’s compressibility and reduce the interface pressure of the rod/target, and thus the striking/protective performance of the rod/target is weakened, respectively. We also conduct an error analysis of the interface pressure and penetration efficiency. With a velocity change of 1.6 times the initial sound speed for the rod or target, the error of the approximate model is very small. For metallic rod–target combinations, the approximate model is applicable even at an impact velocity of 12 km/s.

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.

Monoclinic Eu 2 O 3 was investigated in a Mao-Bell type diamond anvil cell using angle dispersive x-ray diffraction up to a pressure of 26 GPa. Pressure induced structural phase transition from monoclinic to hexagonal phase was observed at 4.3 GPa with 2% volume collapse. Birch –Murnaghan equation of state fit to the pressure volume data yielded a bulk modulus of 159(9) GPa and 165(6) GPa for the monoclinic and hexagonal phases respectively. Equation of state fitting to the structural parameters yielded an axial compressibility of β a > β c > β b for the parent monoclinic phase, showing the least compressibility along b axis. Contrary to the available reports, an anomalous lattice compressibility behavior is observed for the high pressure hexagonal phase, characterized by pronounced hardening of a axis above 15 GPa. The observed incompressible nature of the hexagonal a axis in the pressure range 15–25 GPa is found to be compensated by doubling the compressibility along the c axis.

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 developed a simple theoretical model to study the effect of pressure, temperature, shape and size on nanomaterials. We used the model to study the Equation of state (EOS) and pressure dependence of lattice parameter of SnO 2­ nanomaterial. We selected SnO 2 as an example because of the fact that the required experimental data are available so that a comparison of the results may be presented. We used the model to study the compression behaviour at room temperature and compared our results with the experimental data as well as with those based on Birch- Murnaghan Equation of state (BMEOS). Our results are found to present a good agreement with the experimental data as well as with those based on BMEOS. Due to the simplicity and applicability of the model, we extended our studies at different temperatures i.e. 300 K, 500 K and 700 K. A shift in the isotherms has been obtained. We also included the effect of shape and size in the EOS model to make it widely applicable for nanosystems. The results of pressure dependence of lattice parameter for SnO 2 are compared with available experimental data. A good agreement between theory and experiment supports the validity of the model developed.

Structural and electronic properties of α, β, δ and e polymorphs of BeH2 are studied. The effect of pressure on these properties is also seen. Investigations are carried out using the linear combination of atomic orbitals method. The lattice parameters, computed by coupling total energy calculations with the Murnaghan equation of state for the four crystals, are overall in agreement with the experimental data and other calculations. Enthalpy-pressure diagram indicates structural phase transitions α → β, α → δ, α → e, β → δ, β → e, and δ → e to occur at 8.75, 12.75, 18.34, 39.53, 55.57 and 76.60 GPa respectively. Electronic band structure and density of states from PBE-GGA show that all polymorphs have wide bandgap. However, quantitative and qualitative agreement of the bandgap from hybrid calculations is observed with available GW data in α-BeH2. Therefore bandgaps from hybrid calculations are also proposed. In the three polymorphs the bandgap decreases slowly with pressure. Beyond 100 GPa, the β structure exhibits overlap of bands at the Γ point.

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.

This study presents structural, elastic and electronic properties of BNFF-1 using density functional theory (DFT). For obtaining correct ground state structure, two different dispersion corrected methods (Grimme (G06) and Tkatchenko-Scheffler (TS)) along with standard DFT functional have been used. The obtained results with TS functional show less deviation (∼1.2%) than G06 (∼1.7%). This small difference could be due to the relative variation in dispersion coefficients incorporated. The structural parameters from van der Waals (vdW) corrected schemes clearly informs about the role of weak interactions and bond polarizability differences on the structural stability of BNFF-1. The calculated bulk modulus and its pressure derivative using third order birch murnaghan equation of state are 11.43 GPa (17.46 GPa: polycrystalline using Hill approximation) and 8.17 respectively. From the magnitude of bulk modulus we can conclude that BNFF-1 is similar to well known energetic material RDX. The order of compressibility of the lattice parameters obtained from the first order pressure coefficient is c > a > b. The study of elastic constants and the related properties of this material has also been carried out to know the impact and frictional sensitivity of this material. At the end, electronic band structure calculation results at TS level, reveal that, BNFF-1 is a direct band gap (3.02 eV) material along Γ-Γ direction in the first Brillion zone. Overall, the effect of bond polarizability through TS-scheme is well addressed in order to understand the various structure-property correlations.

Theoretical calculations are performed to investigate the electronic structure, structural phase stability and optical properties of double perovskite oxide semiconductors namely Sr2AMoO6 (A= Mg, Zn) in tetragonal symmetry using WIEN2k. In order to estimate the ground state parameters, total energies are calculated with respect to molecular volume and the energies are fitted with Brich – Murnaghan equation of state. The estimated ground state parameters are comparable with the available experimental data. The band structure calculations for these compounds reveal that these compounds exhibit semiconducting behaviour with an indirect band gap. To explore the optical transitions in these compounds, the real and imaginary parts of the dielectric function are analyzed at ambient conditions and the important optical constants are calculated.

The sound velocity (V P) of liquid Fe–10 wt% Ni and Fe–10 wt% Ni–4 wt% C up to 6.6 GPa was studied using the ultrasonic pulse-echo method combined with synchrotron X-ray techniques. The obtained V P of liquid Fe–Ni is insensitive to temperature, whereas that of liquid Fe–Ni–C tends to decrease with increasing temperature. The V P values of both liquid Fe–Ni and Fe–Ni–C increase with pressure. Alloying with 10 wt% of Ni slightly reduces the V P of liquid Fe, whereas alloying with C is likely to increase the V P. However, a difference in V P between liquid Fe–Ni and Fe–Ni–C becomes to be smaller at higher temperature. By fitting the measured V P data with the Murnaghan equation of state, the adiabatic bulk modulus (K S0) and its pressure derivative (K S ′ ) were obtained to be K S0 = 103 GPa and K S ′ = 5.7 for liquid Fe–Ni and K S0 = 110 GPa and K S ′ = 7.6 for liquid Fe–Ni–C. The calculated density of liquid Fe–Ni–C using the obtained elastic parameters was consistent with the density values measured directly using the X-ray computed tomography technique. In the relation between the density (ρ) and sound velocity (V P) at 5 GPa (the lunar core condition), it was found that the effect of alloying Fe with Ni was that ρ increased mildly and V P decreased, whereas the effect of C dissolution was to decrease ρ but increase V P. In contrast, alloying with S significantly reduces both ρ and V P. Therefore, the effects of light elements (C and S) and Ni on the ρ and V P of liquid Fe are quite different under the lunar core conditions, providing a clue to constrain the light element in the lunar core by comparing with lunar seismic data.

We present an ab-initio theoretical study of structural and elastic properties of GaAs1−xBix alloys in the Zinc-Blende (ZB) phase. We use a recent version of Wien2k package code based on Density Functional Theory (DFT) Full Potential and Linearized Augmented Plane Waves (FP-LAPW) method including recent Tran-Blaha modified Becke–Johnson correction of the exchange potential (TB-mBJ) and the spin–orbit interaction (SO). The calculations are performed within the Local Density Approximation (LDA) as well as the Generalized Gradient Approximation (GGA). We study first the structural properties of GaAs1−xBix alloys by solving Murnaghan equation of state. Our results show that the ZB phase is the lowest equilibrium crystal structure of GaAs1−xBix in the whole alloy composition range, in agreement with previous theoretical predictions. The variations versus Bi contents of the ZB GaAs1−xBix lattice constant a0, bulk modulus B0 and its pressure derivative B 0 ′ are also found very close to other theoretical and experimental data, but with much smaller bowing effects indicating a better resolution thanks to TB-mBJ correction. The variations of B0 versus the reverse equilibrium volume of the unit cell (1/V0) are found to be described by the simple linear empirical expression B0 = −0.21068 + 0.16695/V0 which is close to the theoretical prediction for III-V semiconductors with, however, somewhat lower linear coefficients values, suggesting a more metallic behavior. In a second part of this work, we use Birch–Murnaghan approach to study the elastic properties of GaAs1-xBix alloys. The elastic stiffness coefficients, C11, C12 and C44, and their variations versus alloy composition were determined for ZB GaAs1−xBix alloy. Their values in GaAs and GaBi binary compounds are found in very good agreement with available experimental and/or theoretical data. Their variations in GaAs1−xBix alloy show a monotonic decrease with increasing Bi contents, indicating a softening behavior as is typically the case for metallic alloys. The values of the bulk modulus derived with the help of C11, C12 and C44 elastic stiffness coefficients are found very close to B0 values derived directly from Murnaghan equation of state, indicating the good accuracy of Cij coefficients deduced from Birch–Murnaghan procedure.

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 phase stability of nanocrystalline Pr2O3 has been investigated under pressure by in-situ high pressure X-ray diffraction using Mao-Bell type diamond anvil cell. The ambient structure and phase of the praseodymium oxide have been resolved unambiguously using x-ray diffraction, SEM and TEM techniques. Under the action of pressure the cubic phase of the system is retained up to 15 GPa. This is unusual as other isostructural rare earth oxides show structural transformations even at lower pressures. From the best fit to the P–V data with the Murnaghan equation of state yields a bulk modulus of 171 GPa.

The dependence of the unit cell volume of BaSnO3 on the pressure up to 15 GPa has been investigated and the constants of the Murnaghan equation of state B0 = 178.39 ± 4.09 GPa and B′0 = 4.68 ± 0.56 have been obtained using the X-ray diffraction method. The change of the isomer shift (IS) in BaSnO3 with a variation in the pressure P has been examined using the gamma resonance method. This quantity is ∂IS(P)/∂P = −(0.00474 ± 0.0002) mm s−1 GPa−1 or, taking into account the measurements of the unit cell parameter under pressure, ∂IS/∂L = 1.42 mm s−1A−1, where L is the tin-oxygen distance.

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.

Article history: Sound velocities of Fe and Fe-S liquids were determined by combining the ultrasonic measurements and synchrotron X-ray techniques under high pressure-temperature conditions from 1 to 8 GPa and 1573 K to 1973 K. Four different liquid compositions were studied including Fe, Fe-10 wt% S, Fe-20 wt% S, and Fe-27 wt% S. Our data show that the velocity of Fe-rich liquids increases upon compression and decreases with increasing sulfur content, whereas temperature has negligible effect on the velocity of Fe-S liquids. The sound velocity data were combined with ambient-pressure densities to fit the Murnaghan equation of state (EOS). Compared to the lunar seismic model, our velocity data constrain the sulfur content at 4 ± 3 wt%, indicating a significantly denser (6.5 ± 0. 5g /cm3) and hotter (1870 + 100 −70 K) outer core than previously estimated. A new lunar structure model incorporating available geophysical observations points to a smaller core radius. Our model suggests a top-down solidification scenario for the evolution of the lunar core. Such "iron snow" process may have been an important mechanism for the growth of

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.

Structural properties of MnS have been studied using plane wave pseudopotential density functional theory as implemented in Quantum Espresso code. Local density approximation (LDA) along with ultrasoft pseudopotential has been used for total energy calculations. The calculated total energies are fitted to Murnaghan equation of state to calculate equilibrium lattice constant, isothermal bulk modulus and pressure derivative of isothermal bulk modulus for NaCl-type structure of MnS and compared with previous experimental and theoretical calculations and good agreement is achieved with those results. Phonon frequencies have also been derived for B1 phase of MnS along high symmetry directions using the density functional perturbation theory at ambient condition.

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.

The first-principles total energy calculations are coupled with the Murnaghan equation of state to predict lattice constant and the bulk modulus of hypothetical B2 crystal structure of CdNb intermetallic. The calculations for structure determination are performed deploying the linear combination of atomic orbitals method within the framework of density functional theory. After settling the structure, electronic properties such as partial density of states, total density of states, two dimensional electron momentum density etc. are calculated. All electronic properties and the Fermi surface are obtained by applying the linear augmented plane wave method. Features of the Fermi surface are interpreted in terms of bands and the two dimensional electron momentum density distribution.

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.

Soft body impact tests were conducted using an artificial bird of 0.2 kg with a striking velocity of 150 m·s−1 on three different configurations of metallic wing leading edge (LE) structures. The objective of these experiments is to address the preliminary design of LE wing structures to soft body impact loads. The explicit finite element software PAM-CRASH was selected to simulate these experiments using smoothed particle hydrodynamics (SPH) techniques for modelling the bird. The impact tests were also performed for a velocity of 70–180 m·s−1 on instrumented aluminium and steel flat plates to attain the bird material parameters. The artificial bird material parameters for a hydrodynamic material model (Murnaghan equation of state) and elastic-plastic solids with damage and failure were optimised using iSIGHT and PAM-CRASH coupling technique in conjunction with tests on flat plates. The experimental and numerical correlations of the flat plates suggested that at high velocity the hydrodynamic material mod...

By first-principle calculation, the electronic structure and magnetic properties of the Mn2ZnSi full-Heusler alloy with CuHg2Ti-type structure are investigated. Calculations show that Mn2ZnSi compound presents half-metallic ferrimagnetic properties under the equilibrium lattice constant. The influence of spin-orbit interaction for the magnetic moments is investigated. The result shows spin-orbit interaction has little influence on magnetic moment. The bulk modulus of Mn2ZnSi obtained by a fit of the Murnaghan equation of state is 134.3 GPa, which is more compressible than some other Heusler alloys. At the pressure range of 0 to 17.7 GPa, Mn2ZnSi presents half-metallic character. Mn2ZnSi would be a promising material for future spintronic applications.

Neutron powder diffraction data have been collected from deuterated ice VI (space groupP42/nmc,Z= 10) at 76 state points in its field of thermodynamic stability above 150 K (approximately 0.6

Structural parameters and electronic bandgaps of two polymorphs of Be3P2 were determined using the first-principles periodic linear combination of atomic orbitals method within the framework of density functional theory implemented in the CRYSTAL code. We studied the tetragonal structure and the cubic O2-type polymorph of Be3P2 which is found to exist at high pressure. Coupling total energy calculations with the Murnaghan equation of state, equilibrium lattice constants and bulk moduli for tetragonal and cubic O2-type Be3P2 are reported. Isothermal pressure-induced structural phase transitions from tetragonal → cubic O2-type and cubic α → cubic O2-type are observed to occur at 25.5 GPa and 217.5 GPa, respectively, from enthalpy calculations. The electronic band structure calculations predict that both tetragonal and cubic O2-type polymorphs of Be3P2 have direct bandgaps of 1.45 eV and 1.22 eV, suggesting utility in IR sensors and detectors. Pressure-dependent band structure calculations were performed to ...

The elastic and structural behaviour of dehydrated analcime in compression in a non-penetrating medium up to 3 GPa was studied in a diamond anvil cell usingin situsynchrotron powder diffraction. A first-order phase transition at 0.4–0.7 GPa is accompanied by a symmetry change from monoclinic (I2/a) to pseudo-rhombohedral (R3) due to trigonalization of the aluminosilicate framework. This is due to the migration of cations to new positions close to the 6-membered rings forming the channels. The reduction of the mean aperture of the structure-forming 6- and 8-membered rings, as a result of tetrahedral tilting, leads to a 7.5% reduction in volume at the phase transition. The bulk modulus values are 38(2) GPa for the low pressure (LP) phase [fitted with a Murnaghan equation of state,K' = 4 (fixed)] and 11(4) GPa for the high pressure (HP) phase [fitted with a third-order Birch–Murnaghan equation of state,K' = 9(1)]. The elastic behaviour of the LPphase is anisotropic, with compressibilities βa:βb:βcin the ratio 1:4:2; the most compressible directionbcoinciding with the orientation of empty 8-membered rings. The compressibility of the HP phase is isotropic. Trigonalization appears to be the most effective (and probably unique) mechanism of radical volume contraction for the ANA structure type.

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.

Using a diamond anvil cell device and synchrotron radiation, the in-situ high-pressure structure of SrMnO3 has been investigated. At pressure up to 28.6 GPa, no pressure-induced phase transition is observed. The lattice parameters as a function of pressure is reported, and the relationship of the axial compression coefficients is ?a > ?c. The isothermal bulk modulus K298=266(4) GPa is also obtained by fitting the pressure-volume data using the Murnaghan equation of state.

The pressure-induced Raman shifts of six vibrational bands of 20% and 50% trans-polyacetylene nanoparticles in poly(vinyl-butyral) matrix films (NPA/PVB) were studied from 0 to 45 kbar using a diamond anvil cell (DAC). The Raman shifts did not depend on the thickness of the two samples studied. Two of the vibrational bands displayed peak positions that depended on the isomeric compositions, with the 20% trans-NPA/PVB bands being slightly blue-shifted relative to the 50% trans-NPA/PVB bands over the 45 kbar pressure range. The Raman bands of NPA/PVB associated with the trans form initially exhibited a relatively large shift at low pressures (P < 10 kbar) along with a drastic change in their band profile. In order to investigate the relative shielding of the vibrational modes studied, a Gruneisen analysis of the pressure-induced shifts was conducted by estimating the parameters of the Murnaghan equation of state for solid polyacetylene (PA). Four of the six vibrational modes were found to be sensitive to compression of the interchain void space, while the other two modes were insensitive, indicating that they are relatively shielded from the compression of the sample. Copyright © 2011 John Wiley & Sons, Ltd.

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.