Structural,elastic, electronic,phonon and thermal properties of Ir3Ta and Rh3Ta alloys

We have studied the structural, elastic, electronic, phonon and thermodynamic properties of Ir₃Ta and Rh₃Ta alloys, using ab initio calculations. For the L1₂ phase, we report the calculated lattice constants, bulk modulus and elastic constants, and these values are compared with previously published values. We also derive the elastic constants from the values of the slopes of the acoustic branches in the phonon dispersion curves. The band structures show that both materials are metallic. The phonon dispersion curves, and their corresponding total and projected densities of states, are obtained using a linear response in the framework of the density functional perturbation theory. The specific heat capacity at constant volume and different temperatures is calculated, and this aspect is discussed using the quasi-harmonic approximation.     

Ab-initio study of the structural,electronic, elastic and vibrational properties of HfX (X = Rh,Ru and Tc)

The structural, elastic, electronic and phonon properties of HfX (X = Rh, Ru and Tc) in the caesium-chloride phase have been investigated using the density functional theory within the generalized gradient approximation. The optimized lattice constant (a₀), bulk modulus (B) and the elastic constants (C_ij) are evaluated. The results are in a good agreement with the available experimental and theoretical data in the literature. Electronic band structures and densities of states have been derived for these compounds. The present band structure calculations indicate that the phases of caesium-chloride HfX (X = Rh, Ru and Tc) compounds are metals. Phonon dispersion curves and their corresponding total and projected density of states have been obtained using the direct method. The phonon spectra suggest that these compounds are dynamically stable in the caesium-chloride phase.     

Investigations of the magnetic,mechanical and thermodynamic properties of cubic phase LaMO3 (M=Ti~Fe)

The magnetic, mechanical and thermodynamic properties of LaMO₃ (M = Ti~Fe) have been systematically investigated using the first-principles calculations. The total magnetic moments of LaMO₃ are mainly from the M atom, and the contributions from La and O are very small. For LaTiO₃, LaVO₃, LaCrO₃ and LaMnO₃ the total magnetic moments agree well with experiment, while with somewhat larger disagreement for LaFeO₃. Using the GGA + U (U = 5.6 eV), the calculated magnetic moment of LaFeO₃ is 4.98μ_B, which is in agreement with experiment data. The elastic constants and Vickers hardness suggest that LaMO₃ are mechanically stable and soft materials. The B/G ratios indicate that all of LaMO₃ are ductile except LaVO₃ and LaCrO₃.The LaCrO₃ has the highest Debye temperature, while LaVO₃ has the lowest Debye temperature.     

Abnormally high residual dislocation density in pure aluminum after Al/Ti/Al laminate annealing for seven days

We report an abnormally high residual dislocation density in aluminium in an Al/Ti/Al laminate annealed at 873 K for seven days. The residual dislocation density reaches 7.5 × 10¹⁴ m^?2, higher than that in aluminum after severe plastic deformation processes such as accumulative roll bonding and high-pressure torsion. It is proposed that the high residual dislocation density may result from obstruction of the movement of TiAl₃ nanoparticles by the grain boundary and Ti atoms conglomerating at vacancies distributed in the aluminium matrix at a high temperature for a sufficient time to allow a relatively stable crystal.     

Basic visual perceptual processes in children with typical development and cerebral palsy: The processing of surface,length, orientation,and position

The present study aims to assess how the processing of basic visual perceptual (VP) components (length, surface, orientation, and position) develops in typically developing (TD) children (n = 215, 4–14 years old) and adults (n = 20, 20–25 years old), and in children with cerebral palsy (CP) (n = 86, 5–14 years old) using the first four subtests of the Battery for the Evaluation of Visual Perceptual and Spatial processing in children. Experiment 1 showed that these four basic VP processes follow distinct developmental trajectories in typical development. Experiment 2 revealed that children with CP present global and persistent deficits for the processing of basic VP components when compared with TD children matched on chronological age and nonverbal reasoning abilities.     

Social identity uncertainty: Conceptualization,measurement, and construct validity

The following paper establishes a measurement of social identity uncertainty. Based on uncertainty-identity theory, we propose social identity uncertainty is a unique type of self-uncertainty related to group identification. We further believe social identity uncertainty is comprised of two components: identity-uncertainty (i.e., uncertainty about one’s group identity) and membership-uncertainty (i.e., uncertainty about being a group member). Study 1 (N = 314) and Study 2 (N = 299) explored and confirmed that two subcomponents exist within social identity uncertainty. Study 3 (N = 295) developed convergent validity using various social identity-related constructs, and discriminant validity using dispositional constructs. Overall, we found (a) identity-uncertainty and membership-uncertainty are distinct constructs, and (b) our measurements have both convergent and discriminant validity.     

Lattice dynamics of ordered and disordered Cu3 Au with a tight-binding potential model

Abstract

The phonon dispersion curves for both ordered and configurationally disordered cubic phases of Cu₃Au are calculated using force constants derived from a many-body tight-binding potential. The derived phonon frequency spectra are used to estimate the vibrational contribution to the entropy difference between the two phases. A brief discussion concerning the relative values of interatomic force constants is included.     

Performance,incentives, and needs for autonomy,competence, and relatedness: a meta-analysis

Although self-determination theory (SDT) is one of the most widely cited theories of human motivation and function, critics have questioned the practical utility of its three needs (i.e., autonomy, competence, and relatedness) in performance contexts. We conduct a meta-analysis (k = 108, N = 30,648) to explore the magnitude and boundary conditions of need satisfaction and performance. As expected, autonomy (ρ = .28), competence (ρ = .37), and relatedness (ρ = .25) predict performance. Incentivization per se has little impact on need-satisfaction: instead, the need satisfaction → performance relationship is moderated by incentive salience. Consistent with a crowding-out hypothesis, need satisfaction matters less to performance when incentives are directly salient (ρ = .22) and more when indirectly salient (ρ = .45). Our meta-analysis demonstrates that indirectly salient incentives and need-satisfaction are indeed compatible, providing a direct response to criticisms of SDT in performance contexts. Additional unexpected findings and future directions are discussed.     

The temperature dependence of the optical dispersion parameters in Si and Ge

Abstract

In Si and Ge, the optical dispersion parameters (single-oscillator energy E_o , dispersion energy E_d and bond energy gap E_g developed by Wemple and DiDomenico, and Phillips) have been analysed in the temperature range 100-300 K using data obtained by Icenogle et al. E_o and E_g exhibit a very small temperature dependence in both materials. The thermal coefficients of the dispersion energy, dE_d/dT, have opposite signs (Si, –41·9 × 10^?4eVK^?1; Ge, +37·7 × 10^?4eVK^?1).     

First principles determination of the Peierls stress of the shuffle screw dislocation in silicon

The Peierls stress of the a/2?110? screw dislocation belonging to the shuffle set is calculated for silicon using density functional theory. We have checked the effect of boundary conditions by using two models, the supercell method where one considers a periodic array of dislocations, and the cluster method where a single dislocation is embedded in a small cluster. The Peierls stress is underestimated with the supercell and overestimated with the cluster. These contributions have been calculated and the Peierls stress is determined in the range between 2.4?×?10^?2 and 2.8?×?10^?2?eV?Å^?3. When moving, the dislocation follows the {111} plane going through a low energy metastable configuration and never follows the 100 plane, which includes a higher energy metastable core configuration.     

Importance of crack-propagation-induced ε-martensite in strain-controlled low-cycle fatigue of high-Mn austenitic steel

We investigated the roles of deformation-induced ε-martensitic transformation on strain-controlled low-cycle fatigue (LCF) through crack-propagation analysis involving a notching technique that used a focused ion beam (FIB) setup on Fe–30Mn–4Si–2Al austenitic steel. Using the FIB notch, we separated the microstructure evolution into macroscopic cyclic deformation-induced and crack-propagation-induced microstructures. Following this, we clarified the fatigue crack-propagation-induced ε-martensitic transformation to decelerate crack propagation at a total strain range of 2%, obtaining an extraordinary LCF life of 1.1 × 10⁴ cycles.     

Solid-solution hardening in dilute and concentrated alloys

Abstract

Numerical analysis of the temperature dependence of the critical resolved shear stress of several binary copper-based alloy single crystals containing 0·11 to 7·6 at.% Mn, 0·01 to 14·0 at.% Al, 0·5 to 8·0 at.% Ge and 5 to 30 at.% Zn, has been carried out in terms of the kink-pair formation model of solid-solution hardening. Several solute atoms are found to be involved in the unit activation process not only in concentrated alloys but also in dilute ones. A single mechanism of solution hardening, which involves the interaction between a dislocation and many solute atoms, is therefore operative in all the alloys referred to above.     

Site preference and alloying effect of Re atoms in the edge dislocation cores in Ni3Al

Using Cambridge sequential total energy package method based on the density functional theory, we investigated the site preference and alloying effect of Re atoms in the [1 0 0] (0 1 0) edge dislocation cores in Ni₃Al. Due to the introduction of a Re atom, the energetic and electronic structure of dislocation core systems have been changed a lot. The binding energy results suggest Re atom prefers Al site, especially the centre site in the centre-Al system, which can be explained by the results of Mulliken orbital population and density of states. When Re atom occupies the centre site in the centre-Al system, the DC system has the highest stability and stronger bonds formed between the Re atom and its nearest neighbouring atom due to hybridization of the Re-5d and Ni-3d orbitals.     

Characterization of Al/n-ZnO/p-Si/Al structure with low-cost solution-grown ZnO layer

We report the fabrication of Al/n-ZnO/p-Si/Al diode structures with a flower-like ZnO layer. The average grain size, microstrain and dislocation density in the ZnO layer were determined as 25?nm, 1.55?×?10^?3 and 3.23?×?10¹³?cm^?2, respectively. From absorption spectra, the optical band gap was found to be ～3.17?eV. A red shift was attributed to non-stoichiometry arising from Zn⁺² ions substituting for oxygen vacancies. The ideality factor was determined as 1.55. The barrier height was calculated as 0.71?eV from I–V characteristics and 0.73?eV using the Norde plots.     

Rational Beliefs as Cognitive Protective Factors Against Posttraumatic Stress Symptoms

The current study investigated the predictions of rational emotive behaviour therapy’s (REBT) model of psychological health that rational beliefs would act as cognitive protective factors against posttraumatic stress responses. The study aimed to contribute original data regarding the role of functional cognitions in the prevention of posttraumatic stress symptomology. A model consistent with REBT’s theory of psychological health was investigated through the use of structural equation modelling among a sample of 309 international emergency service personnel who had all been exposed to a significant life trauma. Results indicated that the REBT model of posttraumatic stress responses was found to be an acceptable fit of the data (χ² = 199.99, df = 94, p < .001; RMSEA = .06 (CI 90 % = .05/.08); SRMR = .05; CFI = .93; TLI = .91) and explained 76 % of variance in posttraumatic stress symptoms. Self-acceptance beliefs and high frustration tolerance beliefs negatively predicted posttraumatic stress responses; non-catastrophizing beliefs positively predicted posttraumatic stress responses; and indirect effects were observed between preference beliefs and posttraumatic stress responses via self-acceptance and high frustration tolerance beliefs. Results suggest that rational beliefs are negatively associated with posttraumatic stress responses and support the REBT model of psychological health. Current results contribute important information regarding the role of functional cognitions in the alleviation of posttraumatic stress symptoms.     

Coping,social support,stigma, and gender difference among people living with HIV in Guangxi,China

The current study examined whether gender, HIV-related stigma, social support, and the interaction between gender and social support are associated with coping responses among people living with HIV and AIDS (PLWHA) in Guangxi, China. A total of 2987 PLWHA in Guangxi participated from October 2012 to August 2013. Multivariate analysis of covariance was conducted with gender and social support as main factors in the model, and stigma and other variables as covariates. After controlling for demographic variables and stigma, there were significant main effects of emotional social support (F = 1.61, p < .001), functional social support (F = 1.67, p < .001), and informational social support (F = 3.67, p < .001) on various coping strategies. The interaction between gender and informational social support (F = 1.33, p < .05), internalized stigma (F = 37.03, p < .001) and perceived stigma (F = 9.16, p < .001) were associated with various coping strategies. Findings signify the importance of HIV-related stigma and social support differences in the coping strategies among PLWHA in Guangxi, China.     

A first-principles study of the formation of θ′′ phase in Al–Cu alloys

The θ′′-Al₃Cu phase plays an important role in the precipitation process of Al–Cu alloys. This phase has a sandwich structure—every two {200}_Cu layers are separated by three {200}_Al layers. To analyse the formation mechanism of this structure, the elastic strain energy of the {200}_Cu and {200}_Al layers, and the chemical bonding energy that reflects the interaction between the electrons in Cu and neighbouring Al atoms are calculated and analysed by first-principles calculations, projected density of states and Bader analysis. Our computation results reveal that this sandwich structure is energetically preferred in the competition of elastic strain and chemical bonding energies. To minimise the elastic strain energy of {200}_Al and {200}_Cu layers, the {200}_Cu layers prefer being apart from each other, whereas the chemical bonding energy favours the opposite arrangement because the intermetallic bond between Al and Cu atoms may form through p-d hybridization.     

Surface tension measurement of undercooled liquid Ni-based multicomponent alloys

The surface tensions of liquid ternary Ni–5%Cu–5%Fe, quaternary Ni–5%Cu–5%Fe–5%Sn and quinary Ni–5%Cu–5%Fe–5%Sn–5%Ge alloys were determined as a function of temperature by the electromagnetic levitation oscillating drop method. The maximum undercoolings obtained in the experiments are 272 (0.15T _L), 349 (0.21T _L) and 363?K (0.22T _L), respectively. For all the three alloys, the surface tension decreases linearly with the rise of temperature. The surface tension values are 1.799, 1.546 and 1.357?N/m at their liquidus temperatures of 1719, 1644 and 1641?K. Their temperature coefficients are ?4.972?×?10^–4, ?5.057?×?10^?4 and ?5.385?×?10^?4?N/m/K. It is revealed that Sn and Ge are much more efficient than Cu and Fe in reducing the surface tension of Ni-based alloys. The addition of Sn can significantly enlarge the maximum undercooling at the same experimental condition. The viscosity of the three undercooled liquid alloys was also derived from the surface tension data.