The Experts below are selected from a list of 177 Experts worldwide ranked by ideXlab platform

Ling-cang Cai - One of the best experts on this subject based on the ideXlab platform.

  • Pressure Dependence of Fusion Entropy and Fusion Volume of Six Metals
    Journal of Chemical & Engineering Data, 2012
    Co-Authors: Qi-long Cao, Pan-pan Wang, Duo-hui Huang, Fan-hou Wang, Ling-cang Cai
    Abstract:

    Molecular dynamics simulations of the melting curves of six metals including Ag, Cu, Al, Mg, Ta, and Mo for the pressure range (0 to 15) GPa are reported. The melting curves of Ag, Cu, Al, and Mg fully confirm measurements and previous calculations. Meanwhile, the melting curves of Ta and Mo are consistent with previous calculations but diverge from laser-heated diamond-anvil cells values at high pressure. Our results suggest that the melting slope at 100 kPa is related to the electronic configuration of the element. In addition, the pressure dependence of Fusion Entropy and Fusion volume are calculated up to 15 GPa. The overall Fusion Entropy is separated into topological Entropy of Fusion (ΔSD) due to the configuration change in melting and the volume Entropy of Fusion (ΔSV) due to the latent volume change in melting. Furthermore, we checked the R ln 2 rule under high pressure, according to which the value of ΔSD is a constant at ambient pressure. Result shows that the value of ΔSD is close to R ln 2 at...

  • Melting curves and Entropy of Fusion of body-centered cubic tungsten under pressure
    Journal of Applied Physics, 2012
    Co-Authors: Chunmei Liu, Xiang-rong Chen, Ling-cang Cai, Fu-qian Jing
    Abstract:

    The melting curves and Entropy of Fusion of body-centered cubic (bcc) tungsten (W) under pressure are investigated via molecular dynamics (MD) simulations with extended Finnis-Sinclair (EFS) potential. The zero pressure melting point obtained is better than other theoretical results by MD simulations with the embedded-atom-method (EAM), Finnis-Sinclair (FS) and modified EAM potentials, and by ab initio MD simulations. Our radial distribution function and running coordination number analyses indicate that apart from the expected increase in disorder, the main change on going from solid to liquid is thus a slight decrease in coordination number. Our Entropy of Fusion of W during melting, Delta S, at zero pressure, 7.619 J/mol.K, is in good agreement with the experimental and other theoretical data. We found that, with the increasing pressure, the Entropy of Fusion Delta S decreases fast first and then oscillates with pressure; when the pressure is higher than 100 GPa, the Entropy of Fusion Delta S is about 6.575 +/- 0.086 J/mol.K, which shows less pressure effect. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733947]

R.n. Rai - One of the best experts on this subject based on the ideXlab platform.

  • Solid–liquid equilibria, thermochemical and microstructural studies of binary organic monotectic and eutectic alloy
    Journal of Thermal Analysis and Calorimetry, 2012
    Co-Authors: K. P. Sharma, R. S. B. Reddi, R.n. Rai
    Abstract:

    The phase diagram of 1,4-dibromobenzene (DBB) with pyrogallol (PG) shows the formation of a monotectic and a eutectic alloys at 0.12 and 0.99 mol fractions of DBB, respectively. The phase equilibrium shows the large miscibility gap region with the upper consolute temperature 159.0 °C at 0.55 mol fraction of DBB. Growth kinetics of pure compounds and their monotectic and eutectic at different undercooling (Δ T ) obey Hillig–Turnbull’s equation: v  =  u (Δ T )^ n . Thermodynamic parameters such as enthalpy of mixing, Entropy of Fusion, interfacial energy, roughness parameters and excess thermodynamic functions were computed based on enthalpy of Fusion values obtained from DSC studies. The Cahn wetting condition is applicable for monotectic alloy. The optical microphotographs of binary alloys show lamellar and dendritic features.

  • Solid-liquid equilibrium and thermochemical studies of organic analogue of metal-nonmetal system: Succinonitrile-pentachloronitrobenzene
    Thermochimica Acta, 2010
    Co-Authors: Shiva Kant, R.n. Rai
    Abstract:

    Abstract The phase diagram of an organic analogue of a metal–nonmetal system, involving succinonitrile–pentachloronitrobenzene, shows the formation of a eutectic and a monotectic. The two immiscible liquid phases are in equilibrium with a single liquid phase and the consolute temperature being 53.5 °C above the monotectic horizontal. The phase equilibrium study confirms the alloy composition of monotectic and eutectic at 0.150 and 0.985 mol fractions of succinonitrile, respectively. The solidification behaviour shows the validity of Hilling–Turnbull equation. The thermal properties such as heat of mixing, Entropy of Fusion, roughness parameter, interfacial energy, grain boundary energy and excess thermodynamic functions for parent components, monotectic and eutectic have been studied using their enthalpy of Fusion values. The effects of solid–liquid interfacial energy on morphological change of monotectic have also been discussed. The microstructure of monotectic shows the lamellar growth along with droplets, however, eutectic infers the vertical growth of lamella.

  • Thermal and dielectric studies on binary organic system: benzil–m-nitroaniline
    Materials Letters, 2001
    Co-Authors: R.n. Rai, Kbr Varma
    Abstract:

    A simple eutectic type phase diagram has been established between benzil and m-nitroaniline (m-NA) system. Enthalpy of mixing, solid–liquid interfacial energy, Entropy of Fusion and excess thermodynamic functions were calculated based on enthalpy of Fusion values, determined by the DSC method. The studies concerning the X-ray powder diffraction and the infrared spectroscopy reveal the composite nature of the eutectic and 5 mol% m-NA added benzil. The dielectric constants of eutectic, 5 mol% m-NA added benzil and parent components decrease with increase in frequency (1 kHz–10 MHz) at 27°C. The dielectric constant values of these composites lie between those of m-NA and benzil. The second harmonic generation efficiencies (measured using Kurtz's powder technique) of the hot-pressed composite samples are less than that of pure m-NA.

  • Studies on physicochemical properties of the eutectic and monotectic in the urea—p. chloronitrobenzene system
    Journal of Crystal Growth, 1996
    Co-Authors: Uma Shanker Rai, R.n. Rai
    Abstract:

    Abstract The phase diagram of an organic analog of a nonmetal—nonmetal-type system involving urea and p. chloronitrobenzene shows the formation of a eutectic (0.982 mole fraction of p. chloronitrobenzene) and a monotectic (0.020 mole fraction of p. chloronitrobenzene) with a liquid miscibility gap in the system. The linear velocity of crystallization ( v ) data determined at different undercoolings ( ΔT ) by measuring the rate of advance of an interface in a capillary obey the Hillig—Turnbull equation, v = u ( ΔT ) n , where u and n are constants depending on the solidification behaviour of the materials involved. From the enthalpy of Fusion of the pure components, the eutectic and the monotectic, enthalpy of mixing, excess thermodynamic functions, Entropy of Fusion and interfacial energy were calculated. Optical microphotographs of the eutectic and monotectic give their characteristic features.

Fu-qian Jing - One of the best experts on this subject based on the ideXlab platform.

  • Melting curves and Entropy of Fusion of body-centered cubic tungsten under pressure
    Journal of Applied Physics, 2012
    Co-Authors: Chunmei Liu, Xiang-rong Chen, Ling-cang Cai, Fu-qian Jing
    Abstract:

    The melting curves and Entropy of Fusion of body-centered cubic (bcc) tungsten (W) under pressure are investigated via molecular dynamics (MD) simulations with extended Finnis-Sinclair (EFS) potential. The zero pressure melting point obtained is better than other theoretical results by MD simulations with the embedded-atom-method (EAM), Finnis-Sinclair (FS) and modified EAM potentials, and by ab initio MD simulations. Our radial distribution function and running coordination number analyses indicate that apart from the expected increase in disorder, the main change on going from solid to liquid is thus a slight decrease in coordination number. Our Entropy of Fusion of W during melting, Delta S, at zero pressure, 7.619 J/mol.K, is in good agreement with the experimental and other theoretical data. We found that, with the increasing pressure, the Entropy of Fusion Delta S decreases fast first and then oscillates with pressure; when the pressure is higher than 100 GPa, the Entropy of Fusion Delta S is about 6.575 +/- 0.086 J/mol.K, which shows less pressure effect. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4733947]

Mohammad Hossein Keshavarz - One of the best experts on this subject based on the ideXlab platform.

  • An improved simple method for prediction of Entropy of Fusion of energetic compounds
    Fluid Phase Equilibria, 2013
    Co-Authors: Mohammad Hossein Keshavarz, Sajjad Zakinejad, Karim Esmailpour
    Abstract:

    Abstract A new general method has been introduced for prediction of Entropy of Fusion of important classes of energetic compounds including polynitro arene, acyclic and cyclic nitramine, nitrate ester and nitroaliphatic compounds. It extends earlier work, which was restricted to nitroaromatic compounds, to estimate Entropy of Fusions of any compound containing at least one of the groups Ar NO2, C NO2, C ONO2 or N NO2 through additive and correcting non-additive functions. The number of nitrogen and oxygen atoms in an energetic compound was used as additive function. For 92 compounds (corresponding to 167 measured values) belong to different types of energetic materials, the root-mean square (rms) deviation of the additive part is 13.5 J/(K mol). The reliability of the new model can be increased by considering one correcting non-additive function for which the value of rms deviation is 10.2 J/(K mol). The predicted outcomes of the new method, by using only additive part or both additive and non-additive functions, give more reliable results as compared to one of the best available methods.

  • A new simple approach to predict Entropy of Fusion of nitroaromatic compounds
    Fluid Phase Equilibria, 2010
    Co-Authors: Mohammad Hossein Keshavarz, Hamid Reza Pouretedal
    Abstract:

    Abstract In this paper, a new model is introduced to predict Entropy of Fusion of nitroaromatic compounds, which can be used for some well-known high explosives such as 2,4,6-trinitrotoluene (TNT) and N-methyl-N,2,4,6-tetranitroaniline (TETRYL). Novel correlation contains two different functions for which elemental composition and symmetry of nitroaromatic compounds are used to present additive and non-additive contributions, respectively. The presence of some molecular fragments may influence the value of non-additive function. The root-mean-square (rms) deviation of predictions of Entropy of Fusion from 66 measured values (corresponding to 61 molecules) is 7.88 J/K mol. The predicted results are compared with one of the best available semi-empirical methods, which show the reliability of the new method is relatively good.

E. H. Trinh - One of the best experts on this subject based on the ideXlab platform.

  • Estimation of the configurational Entropy of Fusion
    Applied Physics Letters, 1995
    Co-Authors: K. Ohsaka, E. H. Trinh
    Abstract:

    The Entropy of Fusion of a metal consists of the configurational and vibrational entropies. A formula is presented to evaluate the configurational Entropy by assuming an amorphous phase to be a frozen liquid that has lost the configurational Entropy but still maintains the vibrational Entropy of the corresponding liquid. The magnitude of the configurational Entropy may provide information on the nature of liquid structures. The evaluation requires the enthalpy of the amorphous phase in addition to those of the liquid and crystalline phases. The illustrative evaluation on the Ni24Zr76 alloy shows that ΔSconf is approximately 1k per atom, where k is the Boltzmann constant, which suggests some degree of clustering of atoms in the liquid.