Gruneisen Parameter Research Articles

First-principles investigations of composition-dependent mechanical properties of zinc-blende constituents of MgxZn1−xSyTe1−y rectangular quaternary system

Mechanical properties of zinc-blende MgxZn1−xSyTe1−y alloys and cationic (Mg) and anionic (S) composition dependence of these properties have been investigated theoretically through First-principles calculations. The elastic stiffness constants increase nonlinearly with increasing sulfur concentration at each fixed magnesium concentration, while each of them reduces with increasing magnesium concentration at each fixed sulfur concentration in any binary–ternary/ternary–quaternary system. Hardness of specimens increases nonlinearly with increasing sulfur concentration at each fixed magnesium concentration, while it reduces with increasing magnesium concentration at each fixed sulfur concentration in any binary–ternary/ternary–quaternary system. Each of the considered specimens is mechanically stable, ductile, elastically anisotropic, fairly compressible and plastic in nature. Blending of covalent and ionic bonding with domination of covalent, bending over stretching in chemical bonds and central character of force between atoms have been observed in each specimen. Computed Debye temperature confirms MgS as the hardest and ZnTe as the softest among all the considered specimens. Computed Gruneisen parameter of each specimen demonstrates anharmonic character of atom–atom interactions in each crystal. Thermal conductivity and melting temperature of each of the considered specimens have also been computed in the present study.

Strategies for Manipulating Phonon Transport in Solids.

In this review, we summarize the recent efforts on manipulating phonon transport in solids by using specific techniques that modify their phonon thermal conductivity (i.e., specific heat, phonon group velocity, and mean free path) and phonon thermal conductance (i.e., transmission probability and density of states). The strategies discussed for tuning thermal conductivity are as follows: large unit cell approach and liquid-like conduction for maneuvering specific heat; rattler, mini-bandgap, and phonon confinement for manipulating phonon group velocity; nanoparticles, nanosized grains, coated grains, alloy (isotope) scattering, selection rules in phonon dispersion, Grüneisen parameter, lone-pair electronics, dynamic disorder, and local static distortion for restricting mean free path. We have also included the discussion on tuning phonon thermal conductance, as thermal conduction can be viewed as a transmission process. Additionally, phonon filtering, ballistic transport, and waveguiding are discussed to alter density of states and transmission probability. We hope this review can bring meaningful insights to the researchers in the field of phonon transport in solids.

First-Principles Prediction of Pressure Dependent Mechanical, Electronic, Optical, and Superconducting State Properties of NaC6: A Potential High-Tc Superconductor

Very recently carbon-rich NaC6 with sodalite-like structure has been predicted to show superconducting transition temperature above 100 K at relatively low applied (compared to high-Tc hydrides) hydrostatic pressures. We have investigated the pressure dependent structural, elastic, electronic, superconducting state, and optoelectronic properties of NaC6 in this study. Some important thermophysical properties have also been explored. The elastic properties along with Poisson's and Pugh's ratios and optoelectronic parameters are investigated for the first time. NaC6 was found to be structurally stable only at high pressures at and above 40 GPa, in agreement with previous study. The compound is highly ductile and the chemical bonding is predominantly metallic in nature. The Debye temperature shows strong pressure dependence. The Gruneisen parameter also exhibits significant pressure dependence. The electronic band structure reveals metallic character and consists of highly dispersive and almost flat bands crossing the Fermi level. Both the electronic density of states at the Fermi level and repulsive Coulomb pseudopotential increase gradually with increasing pressure in the range 40 GPa to 70 Gpa. The degree of dispersion in the E(k) curves depend weakly on pressure both in the valence and conduction bands. The optical parameters spectra, studied for the first time, correspond well with the electronic band structure. NaC6 absorbs and reflects electromagnetic radiation quite efficiently in the mid-ultraviolet region. Superconducting transition temperatures of NaC6 have been estimated at different pressures and compared with previously reported values. The effects of various parameters on Tc have been discussed in details.

Thickness-dependent anisotropic transport of phonons and charges in few-layered PdSe2.

So far, layered PdSe2 has attracted much attention due to its completely tunable band-gap with varying layer numbers, yet the thickness-dependent transporting properties have been rarely studied. We have systematically studied the electronic structures, phonon and charge transport properties, and thermoelectric properties of few-layered (from 1L to 4L) and bulk PdSe2 by first-principles calculations and Boltzmann transport theory. As the thickness increases, the energy levels of band edges relative to 4s of selenium move oppositely due to their different bonding states, leading to the power-law decrease of the band-gap. Meanwhile, the electron effective mass decreases rapidly while the hole effective mass increases significantly compared with those unperturbed. Calculations on elastic constants reveal that both bulk and few-layered PdSe2 are mechanically stable, and the bulk is ductile with a Poisson's ratio of 0.27. The shifts of Raman active modes with respect to the thickness as well as their Gruneisen parameters are analyzed and the underlying physics is discussed. At room temperature, the thermal conductivities of the bulk are 7.7, 10.1 and 0.9 W m-1 K-1 along the a, b and c axes, respectively. It is found that the low-frequency modes (<2.0 THz) contribute about 80% of in-plane thermal conductivities. Due to the enhanced contribution from the ZA mode, the thermal conductivity of few-layered PdSe2 is much larger than that of the bulk. The ZA mode is mainly scattered by itself and the Umklapp scattering dominates in the process as the thickness increases. Calculations on charge transport reveal that the electron mobility increases from 2.5-13.2 (1L) to 121.9-167.8 (4L) cm2 V-1 s-1 with the decreasing anisotropy μb/μa, while the hole mobility remains to be ∼20 cm2 V-1 s-1, which is in good agreement with the experimental results. Calculations on the thermoelectric properties reveal that the ZT value as well as the power factor increases largely as the thickness increases and it gets to be optimum for the triple layer. Interestingly, the transport of electrons and phonons is decoupled along the out-of-plane direction, which makes bulk PdSe2 exhibit good thermoelectric performance along the c axis.

Research on the Influence of Temperature and Pressure on Volume, Enthalpy, Entropy, Debye Temperature, Electrical Resistivity, Thermal Conductivity and Thermal Diffusivity of AU with FCC Structure

The melting temperature, the jumps of volume, enthalpy and entropy at the melting point, the isothermal compressibility, the thermal expansion coefficient, the heat capacity at constant volume, the Gruneisen parameter, the Debye temperature, the electrical resistivity, the thermal conductivity and the thermal diffusivity for FCC defective and perfect metals are studied by combining the statistical moment method (SMM), the limiting condition of the absolute stability of the crystalline state, the Clapeyron-Clausius equation, the Debye model, the Gruneisen equation, the Wiedemann-Franz law and the Mott equation. Our numerical calculations of obtained theoretical results are carried out for Au under high temperature and pressure. The SMM calculated melting curve of Au is in good agreement with experiments and other calculations. Our calculations for the jumps of volume, enthalpy and entropy, the thermal conductivity and the thermal diffusivity of Au predict and orient experimental results in the future.

Cationic and anionic composition-dependent mechanical and thermal properties of zinc-blende specimens under $${\hbox {Mg}}_{x} {\hbox {Zn}}_{1\hbox {-}x} {\hbox {S}}_{y} {\hbox {Se}}_{1\hbox {-}y}$$ quaternary system: calculations with density functional FP-LAPW scheme

Elastic and thermal properties of zinc-blende $${\hbox {Mg}}_{x} {\hbox {Zn}}_{1\hbox {-}x} {\hbox {S}}_{y} {\hbox {Se}}_{1\hbox {-}y}$$ quaternary alloys and their constituent binary/ternary compounds have been computed through first principles calculations. Elastic stiffness constants of specimens have been increased almost linearly with increasing sulfur composition at any fixed magnesium composition, while reverse trends have been observed with increasing magnesium composition at any fixed sulfur composition in each binary–ternary/ternary–quaternary system. Hardness of specimens has been increased almost linearly with increasing sulfur composition at any fixed magnesium composition, while it has been decreased with increasing magnesium composition at any fixed sulfur composition in each system. Mechanical stability, elastic anisotropy, compressibility, ductility and plasticity have been observed in each compound. Mixture of covalent and ionic bonding with prominent role of covalent nature, dominating role of bond bending over stretching and central nature of interatomic forces have been investigated in each compound. Interaction between the atoms in any compound has been observed to be anharmonic in nature via calculated Gruneisen parameter. Computed Debye temperature, Debye frequency, thermal conductivity and melting temperature of all the specimens have also been reported.

An X-ray diffraction and Raman spectroscopic study of the high-pressure behavior of gaspéite (Ni0.73Mg0.27CO3)

Here, we present new measurements of the phase stability and lattice compressibility of gaspeite (NiCO3) to 50 GPa. Our study is motivated by our interest in understanding high-pressure carbonate behavior. While carbonates have been extensively studied under high-pressure and -temperature conditions, they exhibit different behaviors. We have studied the high-pressure behavior of gaspeite using diamond anvil cells, Raman spectroscopy, and X-ray diffraction. Our experimental data show that gaspeite maintains the calcite structure up to 50 GPa, reverts to its zero-pressure volume on decompression with little hysteresis, and can be fit by a 3rd-order Birch–Murnaghan equation of state. We calculate a bulk modulus (K0T) of 136(4) GPa and a K′ value of 4.6(3). Additionally, we have determined the isothermal Gruneisen parameter for each of the traced Raman modes. These results contribute to growing experimental evidence that suggests some carbonates can be stable at lower mantle conditions. Ultimately, information in this dataset may facilitate predictions of mixing energetics amongst the calcite-structured carbonates, and therefore help determine the role of carbonates in the transition metal geochemistry of the deep Earth.

Gruneisen parameters of bead-spring chains: MD simulation and theory.

Molecular Dynamics (MD) simulations were carried out in a microcanonical ensemble to compute the Gruneisen parameter (denoted as γ) of a liquid of bead-spring chains having 10 beads/chain. γ was studied over a wide range of temperatures below and above the glass transition temperature. We found that the Gruneisen parameter varied in the range of 2.1-3.1 and was significantly higher than typically observed experimentally in real polymers. In the glass, a theory was developed for γ using a cell model in which the beads are harmonically bound to their respective cell centers. The resulting Gruneisen parameter is predicted to increase slightly with temperature. Above the glass transition temperature, we employed the generalized Flory dimer equation-of-state and the polymer reference interaction model theory to calculate γ. In these calculations, we found that γ decreased with temperature in the liquid. The theoretical predictions for γ were found to be in good qualitative agreement with our MD simulations, without any adjustable parameters, both above and below Tg. In experiments on real polymers, γ undergoes a sharp discontinuity at the glass transition. By contrast, in our MD simulations, γ varies smoothly over a broad transition region.

Analysis of Thermodynamic and Volume Expansion Properties of Nacl Solid at High Temperatures and Pressures

In the present study, we derived new relationship and expression for temperature dependence of thermal pressure for NaCl crystal. A mostly elastic property of solid depends on the strength of inter atomic forces of solids. The present work approach has been developed on the temperature dependence of thermal pressure for NaCl crystal at atmospheric pressure and volume expansion ratio at high temperature. So far our work has been concerted on thermal pressure is dependent of temperature and diverges it’s linearly in high temperature volume expansion ratio through effect of temperature. A close data and Gruneisen parameter is found to be in close agreement with investigational and theoretical shows the standing of present study.

Elastic, Mechanical and Ultrasonic Properties of Nanostructured IIIrd Group Phosphides

Despite the large number of III–V semiconductor studies reported every year at bulk level, the III–V material characterization at nanoscale is still required to evaluate their potential industrial applications in nanoscale electronic devices, optoelectronic devices, chemical, biosensors, etc. In this work, the non-destructive evaluation-based ultrasonic theoretical approach for the material characterization of nanostructured IIIrd group phosphides, namely indium phosphide (InP), aluminum phosphide (AlP), gallium phosphide (GaP), and boron phosphide (BP) with wurtzite crystal phase, has been reported. The second- and third-order elastic constants (SOECs and TOECs) for IIIrd group phosphides have estimated using the Lennard–Jones potential. The mechanical properties and the ultrasonic investigation of the IIIrd group phosphides materials, e.g., ultrasonic velocities, Gruneisen parameters, acoustic coupling constants, and ultrasonic attenuation, have been performed using the estimated values of SOECs and TOECs. The present investigation indicates that the ultrasonic attenuation of IIIrd group phosphides is influenced by the wave velocities and the chosen material’s thermal conductivity. The other thermophysical parameters like the crystal energy density, the specific heat per unit volume, thermal conductivity, and the Debye temperature of these materials have also been reported at room temperature (300 K). The results indicate that BP is the most robust material and has superior elastic, mechanical, and thermal characteristics.

Stability and Lattice Dynamics of Ruddlesden–Popper Tetragonal Sr2TiO4

We report a combined experimental and theoretical lattice dynamics study of the Ruddlesden–Popper layered compound Sr2TiO4. From inelastic neutron scattering experiments, we derive the generalized phonon density of states of Sr2TiO4. We also report its heat capacity, thermal expansion, and thermodynamic Gruneisen parameters using the calculated bulk modulus and find a large value of about 2. Using Raman scattering experiments under pressure, we discuss a potential structural distortion of the tetragonal structure above 11 GPa, which could be due to nonhydrostatic compression. The mode Gruneisen parameters of the four Raman-active modes are determined and shown to be in reasonable agreement with those obtained by density functional perturbation theory (DFPT) calculations. The temperature behavior of the Raman-active modes was studied, allowing us to determine the implicit volume and explicit anharmonic contributions. Above 400 K, the implicit volume contribution dominates the temperature-induced variation of the four Raman-active modes, whereas, below this temperature, the explicit anharmonic contribution is the dominant contributor to the highest energy mode. Our results underline the importance of anharmonicity in vibration-related properties of Sr2TiO4.

Shock propagation behaviour and determination of Gruneisen state of equation for pultruded polyester/glass fibre-reinforced composites

Polyester fibres reinforced with glass fibres hybridised polyester resin composite (PFR/GFHC) is a unconventional complex high-molecular weight crosslinked network polymer composite. This novel composite can be used in the manufacture of structural body parts for lightweight vehicles, armour vest for body protection as well as armours for vehicles. For body armour applications, it is important to determine the dynamic behaviour of PFR/GFHC during high velocity impact. In this work, we propose a method of calculating Gurneisen parameter from the measured Hugoniot in shock velocity – particle velocity of polyester based composites product by high velocity actuated nail gun impact. Several high-velocity impacts were conducted on pultruded plates using a power actuated nail gun with different cartridges and varying nail sizes. The experimentally measured Hugoniot in shock velocity – particle velocity space was determined as Us = 2.872 + 1.22Up (ρ0 = 1.25 g/cc) and low gradient observed for Gruneisen parameter as calculated from measured Hugoniot against V0/V shows higher shock absorption of PFR/GFHC for impact velocity.

Pressure-Induced Phase Transition in Mn(Ta,Nb)2O6: An Experimental Investigation and First-Principle Study.

The high-pressure and high-temperature behaviors of manganotantalite Mn(Ta,Nb)2O6 have been investigated by single-crystal X-ray diffraction and Raman spectroscopy combined with diamond anvil cell technique, as well as first-principle calculations. A pressure-induced reversible phase transition of manganotantalite occurs at 9.5 GPa and room temperature, accompanied by a large volume collapse (∼7.0%) and drastic color change from brownish-yellow to red. The space groups of low-pressure (LP) and high-pressure (HP) phases are the same (Pbcn), but the coordination numbers of Mn increase from six to eight and Ta increase from six to seven, respectively. The band gap becomes narrow from 2.37 to 1.59 eV. We determined the P-T phase diagram of manganotantalite with a positive Clapeyron slope of dP/dT = 0.0073 GPa/K. The P-V data were fitted to a second-order Birch-Murnaghan equation of state with B0 = 149(4) GPa for the LP phase and B0 = 188(3) GPa for the HP phase. The isothermal Grüneisen parameters were determined to be 0.23∼2.03 of the LP phase and 0.59∼0.86 of the HP phase for Raman modes. High-pressure behaviors of Mn(Ta,Nb)2O6 indicate that this kind of material is a potential effective pressure sensor to monitor pressure change or warn pressure abnormality.

On the shock dynamics of weak converging shock waves in solid materials

We presented a geometrical shock dynamics model to predict the behavior of weak converging shock waves in solid materials. Taking into consideration Mie–Gruneisen equation of state the analytical solution is obtained for the flow behind the converging shock-front propagating in solids. The analytical formaluas are also obtained for the shock velocity, pressure, density, particle velocity, temperature, speed of sound, adiabatic bulk modulus, and change-in-entropy behind or across the weak converging shock wave. For this it was assumed that the medium is a homogeneous and isotropic, and the disturbances behind the front do not overtake the converging shock waves. The effects due to an increase in (i) the propagation distance from the axis or centre of convergence, (ii) the Gruneisen parameter, and (iii) the material parameter, are explored on the shock velocity and quantities in the shocked titanium, brass, tantalum, iron, stainless steel 304, aluminum 6061-T6 and OFHC copper. The geometrical shock dynamics model provided a clear picture of whether and how the properties of solids are affected due to the passage of converging shock inside the solid materials.

Anharmonic phonon damping enhances theTcof BCS-type superconductors

A theory of superconductivity is presented where the effect of anharmonicity, as entailed in the acoustic, or optical, phonon damping, is explicitly considered in the pairing mechanism. The gap equation is solved including diffusive Akhiezer damping for longitudinal acoustic phonons or Klemens damping for optical phonons, with a damping coefficient which, in either case, can be directly related to the Gruneisen parameter and hence to the anharmonic coefficients in the interatomic potential. The results show that the increase of anharmonicity has a strikingly non-monotonic effect on the critical temperature $T_{c}$. The optimal damping coefficient yielding maximum $T_c$ is set by the velocity of the bosonic mediator. This theory may open up unprecedented opportunities for material design where $T_{c}$ may be tuned via the anharmonicity of the interatomic potential, and presents implications for the superconductivity in the recently discovered hydrides, where anharmonicity is very strong and for which the anharmonic damping is especially relevant.

Изменение свойств железа при ОЦК-ГЦК-фазовом переходе

Using the previously developed method for calculating crystal properties based on the Mie–Lennard-Jones pair potential, the thermodynamic properties of the BCC and FCC phases of iron at the temperature of the polymorphic BCC-FCC phase transition are calculated. 23 properties of iron and their changes during the BCC-FCC transition are calculated. Calculations have shown that properties such as the Gruneisen parameter, the coefficient of thermal expansion, and the heat capacity practically do not change during the BCC-FCC transition. The elastic modulus, specific entropy, Poisson's ratio, and specific surface energy change in the same way as the molar volume, i.e. within 1%. The Debye temperature and its pressure derivative decrease at the BCC-FCC transition in the same way as the distance between the centers of the nearest atoms increases, i.e. within 2-3%. Based on the analysis of experimental data known from the literature, it is shown that even relatively accurately measured parameters such as the coefficient of thermal expansion and elastic modulus are measured with an error exceeding the values of jumps in these parameters at the BCC-FCC transition. It is indicated that amorphization or nanostructuring of a certain portion of iron during the BCC-FCC transition can contribute to changes in the properties of iron during this phase transition.

Discovering Electron-Transfer-Driven Changes in Chemical Bonding in Lead Chalcogenides (PbX, where X = Te, Se, S, O).

Understanding the nature of chemical bonding in solids is crucial to comprehend the physical and chemical properties of a given compound. To explore changes in chemical bonding in lead chalcogenides (PbX, where X= Te, Se, S, O), a combination of property-, bond-breaking-, and quantum-mechanical bonding descriptors are applied. The outcome of the explorations reveals an electron-transfer-driven transition from metavalent bonding in PbX (X = Te, Se, S) to iono-covalent bonding in β-PbO. Metavalent bonding is characterized by adjacent atoms being held together by sharing about a single electron (ES ≈ 1) and small electron transfer (ET). The transition from metavalent to iono-covalent bonding manifests itself in clear changes in these quantum-mechanical descriptors (ES and ET), as well as in property-based descriptors (i.e., Born effective charge (Z*), dielectric function ε(ω), effective coordination number (ECoN), and mode-specific Grüneisen parameter (γTO )), and in bond-breaking descriptors. Metavalent bonding collapses if significant charge localization occurs at the ion cores (ET) and/or in the interatomic region (ES). Predominantly changing the degree of electron transfer opens possibilities to tailor material properties such as the chemical bond (Z*) and electronic (ε∞ ) polarizability, optical bandgap, and optical interband transitions characterized by ε2 (ω). Hence, the insights gained from this study highlight the technological relevance of the concept of metavalent bonding and its potential for materials design.

Negative thermal expansion in solid deuteromethane

The thermal expansion at constant pressure of solid CD4 III is calculated for the low-temperature region where only the rotational tunneling modes are essential and the effect of phonons and librons can be neglected. It is found that in mK region there is a giant peak of the negative thermal expansion. The height of this peak is comparable or even exceeds the thermal expansion of solid N2, CO, O2, or CH4 in their triple points. It is shown that like in the case of light methane, the effect of pressure is quite unusual: as evidenced from the pressure dependence of the thermodynamic Gruneisen parameter (which is negative and large in the absolute value), solid CD4 becomes increasingly quantum with rising pressure.

On the Applicability of Lindemann’s Law for the Melting of Alkali Metals

The experimental melting data for alkali metals reported in the literature reveal that the melting temperature becomes maximum at a particular value of high pressure and then decreases with the increase in pressure. We demonstrate in the present communication that the Lindemann law does not yield negative values for the melting slopes of solids at high pressures as far as the bulk modulus increases and the Gruneisen parameter decreases with the increase in pressure such that the pressure derivative of bulk modulus and the Gruneisen parameter remain positive finite. Arafin and Singh have produced an agreement with the experimental melting data for alkali metals with the help of the Lindemann law using quadratic equations in powers of pressure for the Gruneisen parameter and bulk modulus. These quadratic equations are shown here to be inadequate and invalid at high pressures. For explaining the negative slopes of the melting curves, we need a theory of melting which should take into account the structural and electronic changes at melting. We present a discussion of some very important and highly relevant studies (Martinez-Canales and Bergara; Deng and Lee) based on fundamental considerations and ab initio calculations used recently for explaining the turnover in the melting curves of alkali metals and ferropericlase, an important Earth lower mantle mineral. The structural and electronic changes are responsible for the anomalous thermoelastic behavior yielding negative values of elastic moduli and Gruneisen parameter both, thus making the Lindemann law applicable to materials under study.

Density functional study of elastic and thermal properties of cubic mercury-zinc-chalcogenide ternary alloys

First principle calculations of elastic and thermal properties of zinc-blende specimens within HgxZn1–xS, HgxZn1−xSe and HgxZn1−xTe ternary systems are executed. Elastic stiffness constants decrease non-linearly with increasing Hg-concentration in each system. Each cubic sample is mechanically and dynamically stable, elastically anisotropic, compressible against elastic deformation, ductile and fairly plastic. Hardness of specimens in each system reduces with enhancement in Hg-composition. Mixed kind of bonding with dominancy of covalent over ionic in most cases, bond bending over stretching and central type of interatomic bonding forces are calculated. In each system, covalency, Debye temperature and frequency, Debye temperature for acoustic phonon, thermal conductivity and melting temperature of specimens decreases, while Philip ionicity and Gruneisen parameter increases with enhancing Hg-concentration.