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Equilibrium sediment volume (ESV) is used as an important parameter for understanding the expansive nature of the bentonites and natural clay soils, for assessing a given bentonite for engineering applications, and for the determination of the type of dominant clay mineral present in a given soil. The ESV is often estimated using different salt solutions to understand the compatibility of given clay soil for long-term engineering application such as landfills. A theoretical approach based on physicochemical behavior of clays was proposed in this paper for the estimation of equilibrium sediment volume of bentonites in the presence of salt solutions. A simple analytical expression relating equilibrium sediment volume with different influencing physicochemical parameters such as clay surface and pore-fluid parameters was presented using the diffuse double layer theory. A quantitative estimation of ESV by the proposed theory was validated on the measured data. A very good agreement between the theoretical and measured data was observed for the commercial bentonite. The theory was in good agreement with the measurements in the concentration range of 0.01 M ≤ n < 1 M for Kutch bentonite while the concentration range was 0.001 M ≤ n < 1 M for Barmer bentonite in NaCl solutions. The influence of different exchangeable cations and the presence of non-clay content on the prediction were analyzed with a great detail using theory and by comparing the ESV data of studied bentonites with the homoionic sodium clay. The parallel plate assumption made in the theory overestimated the ESV data in CaCl2 solution. The proposed analytical model is very useful for understanding the influencing parameters on the bentonite behavior.

Using the first-principles density functional calculations, the structural, electronic and magnetic properties of the Fe 2 XAl (X=Cr, Mn, Ni) compounds in both the Hg 2 CuTi and Cu 2 MnAl-type structures were studied by the full-potential linearized augmented plane waves (FP-LAPW) method. The exchange and correlation potential is treated by the generalized-gradient approximation (GGA) where the results show that the Cu 2 MnAl-type structure is energetically more stable than the Hg 2 CuTi-type structure for the Fe 2 CrAl and Fe 2 MnAl compounds at the equilibrium volume. The full Heusler compounds Fe 2 XAl (X=Cr, Mn) are half-metallic in the Cu 2 MnAl-type structure. Fe 2 NiAl has a metallic character in both CuHg 2 Ti and AlCu 2 Mn-type structures. The total magnetic moments of the Fe 2 CrAl and Fe 2 MnAl compounds are 1.0 and 2.0 μ B , respectively, which are in agreement with the Slater–Pauling rule M tot =Z tot − 24.

We present calculations of the structural, elastic and electronic properties of nonferrous Ti, Zr, and Hf pure metals in both parent and martensitic phases in bcc and hcp structures respectively. They are based on the generalized gradient approximation (GGA) within the density functional theory. The shear modulus, Young's modulus and Poisson's ratio for Ti, Zr, and Hf metals have were calculated and compared with the corresponding experimental values. Using elastic constants obtained from calculations under the GGA, the bulk modulus along the crystallographic axes of single crystals is calculated. This is in good agreement with experiment for Ti and Zr, whereas the hcp structure for Hf is a prediction. At zero temperature and zero pressure, the bcc crystal structure is found to be mechanically unstable for Ti, Zr, and Hf. In our calculations the hcp structure is correctly found to be stable at the equilibrium volume. In the electronic density of states, the smaller n(EF) is, the more stable the compound is, in agreement with the results obtained from the total energy minimum.

The precipitation of topologically close packed (TCP) phases is detrimental for the high temperature strength of high refractory Ni-based superalloys. The beneficial influence of Ru with respect to this so called instability is nowadays well accepted. In the present paper the precipitation of topologically close packed (TCP) phases is studied quantitatively in two experimental alloys (one Ru-free and one with addition of Ru) to clarify the mechanism of the Ru effect. It is confirmed that the TCP phase precipitates undergo sequential phase transformation with the tetragonal σ-phase precipitating first. Ru retards the phase transformation and leads to decreased equilibrium volume fraction of TCP phases. The results clearly indicate that Ru decreases the driving force for TCP phase precipitation. Investigations of crystallography and chemistry of the TCP/matrix interface point to an additional effect by increase of misfit strain energy.

In an effort to establish a scientific foundation for the computational development of advanced Mg-based alloys, a systematic study of the generalized stacking fault (GSF) energy curves has been undertaken. Additionally, the associated stable and unstable stacking and twinning fault energies, ideal shear strengths, and comparative twinnability have been investigated in terms of first-principles calculations for dilute Mg-based alloys of type Mg 95 X. These GSF properties are predicted using the simple and especially the pure alias shear deformations on the basal (0 0 0 1) plane and along the [ 1 0 1 ¯ 0 ] direction of the hexagonal close-packed (hcp) lattice. Fourteen alloying elements (X) are considered herein, namely Al, Ca, Cu, La, Li, Mn, Sc, Si, Sn, Sr, Ti, Y, Zn and Zr. The following conclusions are obtained: (i) the fault energies and the ideal shear strengths of Mg 95 X alloys decrease approximately linearly with an increasing equilibrium volume of X (or Mg 95 X), with the exceptions being for alloying elements Al, Cu, Si and Zn; (ii) alloying elements Sr and La greatly increase the twin propensity of hcp Mg, while Mn, Ti and Zr exhibit opposite trends; and (iii) the observed variation in GSF properties for hcp Mg caused by alloying elements X can be directly traced to the distribution of the differential charge density (Δ ρ )—a spherical distribution of Δ ρ facilitates the redistribution of charge and shear deformation, resulting in lower shear-related properties, such as stacking fault energy and ideal shear strength. Computed GSF properties of Mg 95 X are shown to agree with available experimental and other theoretical results in the literature.

In this paper, we have investigated the electronic, optical and mechanical properties of the Y 2 O 3 crystal by first-principle calculations based on the density–functional theory. The generalized gradient approximation (GGA-PBE) and hybrid exchange–correlation functional (HSE06) are both used for comparative study. It is found that, the band gap of Y 2 O 3 calculated by HSE06 method (6.0 eV) is in good agreement with the experimental band gap data (5.5 eV), and HSE06 gives better electronic structure description close to experiments. Then we calculate the elastic constants, and derive the corresponding properties i.e.; bulk, shear and Young’s moduli, and Poisson’s ratio. Our calculated elastic and mechanical properties correspond well with experimental data. Besides, we also obtain the equilibrium lattice and bulk modulus of yttria by fitting the Birch–Murnaghan equation of state. It is found that, the HSE06 well reproduce the experimental lattice parameters, equilibrium volume and bulk modulus of Y 2 O 3 . Based on the accurate described crystal and electronic structure and mechanical properties by HSE06 method, the optical properties of this material are also analyzed.

The phase decomposition and morphology evolution in thermal aging Fe–Cr alloys were investigated using the phase field method. In the simulation, the effects of atomic mobility, applied strain, alloy concentration and aging temperature were studied. The simulation results show that the rate of phase decomposition is influenced by the aging temperature and the alloy concentration, the equilibrium volume fractions ( V f e ) of Cr-rich phase increases as aging temperature rises for the alloys of lower concentration, and the V f e decreases for the alloys with higher concentration. Under the applied strain, the orientation of Cr-rich phase is intensified as the aging temperature rises, and the stripe morphology is formed for the middle concentration alloys. The simulation results are helpful for understanding the phase decomposition in Fe–Cr alloys and the designing of duplex stainless steels working at high temperature.

A heterophase polydomain structure capable of providing large electromechanical responses was recently discovered in BiFeO 3 epitaxial ferroelectric films. In this work, the energetics of such a microstructure are analyzed to predict the equilibrium volume fraction of domains at different film–substrate lattice misfits, which is a function of the substrate lattice parameters as well as the film thickness. The results from this work provide a theoretical starting point for designing and engineering elastic polydomains in BiFeO 3 thin film materials.

Basic concepts from the multi-reference state formalism for determining the functions for the modified embedded atom method (MEAM) are adopted to modeling elemental plutonium (Pu). In the case of elemental Pu, the focus is on the background electron density. Here we utilize a portion of the formalism that determines the structure of the background density necessary to capture correct phase ordering between fcc and ideal hcp crystal structures. The critical information comes from cold curves, that is the energy/volume relationships, for these phases. Practically speaking, the energy difference between these two phases determines the stacking fault energy of the material. At the same time, the simple monoclinic phase of elemental Pu also becomes higher in energy at the equilibrium volume of the fcc phase. The new model is based on first-principles electronic structure calculations and captures the basic phase ordering of those calculations.

Based on first-principles calculations within the projector augmented wave method and the generalized gradient approximation, the structural, thermodynamic as well as phonon properties of Al–Mn compounds have been investigated. The compounds studied include Al12Mn, Al6Mn, Al8Mn5, Al10Mn3, Al11Mn4 (low temperature phase), γ-AlMn, e-AlMn, and τ-AlMn. Besides phonon calculations, Debye model is also used to evaluate the thermodynamic properties at elevated temperatures, which are compared with available data from experiments and thermodynamic modeling. A good agreement is found between first-principles calculations and experimental values or CALPHAD-type calculations. For Al–Mn compounds with lower Mn content, it is observed that (i) the equilibrium volume decreases roughly linearly while the bulk modulus increases roughly linearly with increasing Mn content, (ii) the bonding strength follows the trend of Al–Al > Al–Mn (and Mn–Mn) at a fixed bond length, and (iii) roughly the higher the Mn content of Al–Mn compounds, the smaller the vibrational contribution to entropy, and in turn, to Gibbs energy. The demonstrated methodology herein, as well as the predicted thermodynamic properties, provides helpful insights into the stability of phases and thermodynamic modeling, especially for system where the experimental information is lacking or less reliable.

First-principles calculations based on density-functional theory were performed for the first time on RTAl (R=Y, Lu, T=Ni, Cu, Pd) compounds. The electronic density of states and equilibrium volume were studied using the relativistic full-potential APW plus local-orbitals calculations and compared with the experimental data available.

The equilibrium volume, compressibility, and coefficient of thermal expansion of B2-based Al–Ni–Ru–M alloys (M = B, Si, Ti, Sc, V, Cr, Mn, Fe, Co, Cu, Zn, Nb, Mo, Tc, Rh, Pd, Zr, Ag, Ta, Hf, W, Re, Os, Ir, Pt, and Au) are determined as a function of concentration of the additive M. Details of the phase structure and determination of these properties are obtained from large-scale simulated annealing of the quaternary alloys using the Bozzolo–Ferrante–Smith method for alloys for the calculation of the energy.

The electronic structure and bonding properties of Laves-phase compounds RV2 (R=Ti, Nb, Hf, and Ta) with C15 structure have been investigated using the full-potential linearized augmented plane-wave method. The results show that the chemical bonding is metallic–ionic–covalent in nature in these compounds, and the covalent bonding between V and V atoms strengthens with the atomic number, increasing among the RV2 (R=Ti, Nb, Hf, and Ta) compounds. The density of states (DOS), equilibrium volume, and elastic properties are discussed, which is important for understanding the physical properties of RV2 (R=Ti, Nb, Hf, and Ta) and may inspire future experimental research.

We study the effect of pressure on the structural and mechanical properties of Pt, Ni and Pd using a first-principle pseudopotential method within the gradient correct approximation of the density functional theory. Our results concerning the effect of pressure on equilibrium volume, elastic constants and bulk modulus were compared with other theoretical calculations and experimental data and are in reasonable agreement.

The effects of physical aging on fracture and yielding behavior are polycarbonate are considered. Two groups of Bisphenol A-based polycarbonate, consisted of extruded PC sheets (thickness of 0.25 mm) and injection molded PC bars (thickness of 3.18 mm) are used. These samples were annealed at various temperatures ranging from 60 to 120 °C, for different times varying up to 240 h. For PC sheets the essential work of fracture (EWF) method was used to analyze fracture behavior. The results are compared to the strain energy density with aging time and aging temperature in the ranges investigated. This effect is confirmed by the change in fracture toughness, as measured by three-point bending tests. The concept of fictive temperature ( T f ) was used to characterize the degree of aging in the sample. T f of a glass in an aged state at a time t is defined as the temperature at which the volume would be equal to the equilibrium volume at T f if the sample were instantaneously removed to that temperature. Differential scanning calorimetry (DSC) was used to determine T f . The variations of T f with aging time and aging temperature are in agreement with both the strain energy density measurement and the three-point bending tests. These results contradict the effects of aging on fracture toughness observed by the essential work of fracture approach. The latter showed anomalous regions of increasing fracture toughness with aging, leading to spurious conclusions. The brittle–ductile transition in fracture behavior is analyzed by an activation energy approach. Aging increases the brittle–ductile transition temperature and the effect is more pronounced for the lower molecular-weight sample. Fracture tests also showed a decrease in the entropy with aging, confirming the results observed previously from tension and compression tests.

We have studied structural, electronic and optical properties of some A II B IV C 2 V ternary semiconductors, precisely CdSiP 2 and CdGeP 2 with chalcopyrite structure which are investigated using the full potential linearized augmented plane wave (FPLAPW) method. For treating the correlation term, we have choosen the local density approximation (LDA). The total-energy approach is used to determine the c / a ratio and the equilibrium volume. On the one hand, we have analyzed electronic properties such as band structures, electronic charge densities and density of states. On the other hand, optical properties are also derived.

The structural and electronic properties of YBa2Cu3O7 have been investigated by the total energy-pseudopotential method within the local density approximation. We have calculated charge density and length of bonds for ambient and high pressures, and the change of hole concentration with pressure in this system. Our results show the increase of holes in both CuO2 planes and Cu–O chains under high pressures. Bulk modulus and equilibrium volume have been also calculated to be 184 GPa and 174.89 A3, respectively.

An algorithm for the calculation of temperature dependent bulk properties of multicomponent systems is introduced and illustrated with the calculation of the coefficient of thermal expansion, equilibrium volume, energy of formation and compressibility of Ni–Ti–Nb shape memory alloys.

In the present work we analyze the electronic structure of Fe 4 C using the linear muffin-tin orbital (LMTO) method. The calculations were carried out for several lattice parameters, and the total energy calculation gives the equilibrium volume. Analysis of the density of states gives a good understanding of the electronic structure and magnetic properties of this compound. The behavior of the magnetic moments, hyperfine field and isomer shift with volume shows some similarities to the related compound Fe 4 N.

The generalized Gordon-Kim method is used to calculate static and dynamic properties of the ionic crystal ScBO3. The equilibrium volume and the crystalline structure are obtained in a good agreement with experimental data. The Raman active phonon modes are calculated by the “frozen phonon” method. The absolute values of these frequencies and its pressure dependence are in good agreement with the experimental data also.

The pressure effect on the solid solubility of the AlSi and AlGe systems is studied using the electronic theory based on pseudo- potentials and the virtual crystal approximation for the disordered alloy. The atomic concentration x -dependence of the equilibrium volume satisfying energy-minimum condition for Al 1− x Si x and Al 1− x Ge x solid solutions with fcc lattice is in good agreement with an available experimental data. The equation of state of these alloy systems is presented quantitatively and the compression effect on the heat of solution is investigated. The heat of solution ΔE S ( x , P ) for Al 1− x Si x and Al 1− x Ge x solid solutions under pressure P is small for the Al-rich region and decreases as the crystal is compressed. Consequently, using the Helmholtz free energy of formation under pressure F ' s ( x , P , T ), we predict the extended solid solutions under pressure in AlSi and AlGe alloy system is consistent with the experimental tendency.

The zero-temperature energies and equilibrium volume expansions of pont-defect free asymmetrical grain boundaries (GBs) in f.c.c. bicrystals have been determined using both an embedded-atom-method potential fitted to Au and a Lennard-Jones potential fitted to Cu. The boundaries chosen involve one of the four densest planes on one side of the interface and a higher-index plane on the other. For both potentials it is found that the two asymmetrical tilt GBs at the endpoints of the GB-energy vs twist-misorientation curves give rise to pronounced energy cusps. These cusps are probably the main reason for the dominating appearance of tilt boundaries in rotating sphere-on-a-plate experiments, in spite of the fact that these boundaries represent an infinitely small subset in the total misorientation space comprised by the five macroscopic parameters needed to specify a general grain boundary. A comparison with earlier work on symmetrical GBs suggests that, except for the two densest lattice planes, symmetrical configurations may have higher energies than asymmetrical GBs with a densest plane on one side of the interface. A practically linear correlation between the energy of a GB and its volume expansion is observed, similar to that for the symmetrical GBs investigated earlier.

The pseudopotential method and the thermodynamic perturbation theory are applied to investigate the thermodynamics of liquid NiAl alloys. Taking into consideration the change transfer within the framework of nonlocal resonant potential model we can rather well describe the equilibrium volume, the energy and the excess entropy of mixing, the dynamic viscosity within the hole concentration interval in the system under consideration.

Shock Hugoniot calculations are carried out for gold using both solid and liquid state theories. The result suggests that shock melting begins to take place at a pressure of 1.2 Mbar. At about 2.1 Mbar, the melting transition is complete. The shock temperature of gold in the liquid phase is substantially lower than that in the corresponding solid phase. The validity of the calculations is tested using equilibrium volume and bulk modulus data, deduced from diamond anvil cell experiments, Hugoniot data and the most recently reported shock temperature data at ∼6 Mbar.

The total energy and the spin moments of YCo 5 are calculated by using the FLAPW method as a function of volume. In contrast to the LMTO-ASA method, the FLAPW method gives the equilibrium volume which agrees with the observation. But, as to the volume dependences of the spin moments both the FLAPW and the LMTO-ASA methods give almost the same results. The orbital moments as well as the spin moments of YCo 5 are studied by carrying out LMTO-ASA calculations with inclusion of the spin-orbit interaction. The results give the correct trend as to the magnitude of the spin and the orbital moments of Co atoms.

Measurements of the electrical conductivity of partially ionised caesium vapour under different pressures and temperatures are reported. Comparisons are made with theoretical predictions based on equilibrium volume ionisation.

The electronic contribution to the pressures which determines the equilibrium volume of transition metals is parametrized by use of the interacting Anderson model. It is discussed that there are two mechanisms which can explain the volume anomalies in the Invar alloys. The Fe-Fe atomic interaction which seems to be important in the Invar effect is also discussed.

Self consistent energy band calculations have been performed for HgTe and CdTe with local density functional potentials, using the LMTO method in the atomic sphere approximation. Equilibrium volumes and bulk moduli are obtained in good agreement with experiment. In the case of HgTe the effect of spin-orbit interation is found to be important in obtaining the equilibrium volume. For both materials the energy bands (although in qualitative agreement with experiment) show a semiconducting gap (inverted in the case of HgTe) which is almost 1 eV lower than experiment. This seems to be a feature common to all calculations for semiconductors using existing local exchange and correlation potentials.

Some recent experimental photoelectron spectroscopic results for the actinide metals are reviewed and compared with the theoretical picture of the basic electronic structure that has been developed for the actinides during the last decade. In particular the experimental data confirm the change from itinerant to localized 5f electron behaviour calculated to take place between plutonium and americium. From experimental data it is shown that the screening of deep core-holes is due to 5f electrons for the lighter actinide elements and 6d electrons for the heavier elements. A simplified model for the full LMTO electronic structure calculations is introduced. In this model the spd and 5f electronic contributions are treated as separable entities. It is shown that the model reproduces quite well the results from the full treatment. The equilibrium volume, cohesive energy and bulk modulus are calculated and compared with experiment. Also the 5f delocalization transition under pressure in Am is treated.