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The four-parameter model has been applied to study the thermodynamic properties like excess free energy of mixing, free energy of mixing, activity coefficients, activity, excess entropy of mixing, entropy of mixing, heat of mixing and microscopic function like concentration fluctuations in the long wavelength limit, SCC(0) of compound forming AlCu liquid alloys at 1373 K. The theoretical data have been compared with the experimental data available in the literature. There is an excellent agreement between the theoretical and experimental data. For the validation of experimental data, the available CALPHAD data have been used to compare the excess free energy of mixing, free energy of mixing, activity of AlCu liquid alloys at 1373 K. For the understanding of the atomic order of liquid alloy, the short-range order parameter has been computed for AlCu liquid alloys at 1373 K. The negative value of short-range order parameter indicates that AlCu liquid alloy at 1373 K is ordering in nature. Again the model parameters are temperature dependent.

The quasi-lattice theory based on the joint effect of size ratio and the energetic (or enthalpic) contribution as well as entropic effect has been applied to study the concentration dependence of the thermodynamic and structural properties of AgCu liquid alloys at 1423 K. The analytical expressions for the thermodynamic properties such as excess free energy of mixing, free energy of mixing, entropy of mixing, heat of mixing and the structural properties like the concentration fluctuations in the long wavelength limit and short range order parameter for a binary liquid alloy have been derived in the framework of quasi-lattice theory. The analytical expressions have been used to compute the various thermodynamic and structural properties of liquid AgCu alloys at 1423 K. The theoretical data of thermodynamic and structural properties have been compared with the available experimental data. The present theoretical investigation successfully explains the observed symmetries in the properties of mixing of liquid AgCu alloys at 1423 K.Further the energy parameter is found to be temperature dependent.

The excess free energies of sub-binary Al–Sn, Sn–Zn and Zn–Al alloys and ternary Al–Sn–Zn alloy were computed using the optimised exponential parameters of R–K polynomial at 973, 1073, 1173 and 127...

The thermodynamic, structural, surface and transport properties of In-Tl binary liquid alloy are studied on the basis of theoretical analysis using the regular solution model at different temperatures. The properties of the alloy at 723 K have been computed by estimating the best fit value of order energy parameter (ω) in the entire range of concentration to match their observed and theoretical values. The values of order energy parameter at different temperatures have been calculated using the value of order energy parameter at 723 K which played key role to study different properties of the alloy using optimization method. The theoretical analysis gives the positive energy parameter (ω), which is found to be temperature dependent.

The alloying behavior of AlMg alloy in the liquid form at 1073 K has been theoretically investigated in the framework of four-parameter model which is based on Maclaurin series. The analytical expressions for thermodynamic functions such as excess free mixing energy, free mixing energy, enthalpy of mixing and entropy of mixing and microscopic functions such as concentration fluctuations at the long wavelength limit and Warren-Cowley chemical short range order parameter have been derived. These expressions have been used to compute the excess Gibbs free energy of mixing, Gibbs free energy of mixing, activity, enthalpy(heat) of mixing, excess entropy of mixing, entropy of mixing, concentration fluctuations in long wavelength limit and Warren-Cowley short range order parameters of AlMg liquid alloys at 1073 K. The investigation shows the excellent concurrence between the experimental and theoretical measurements of the mixing properties of AlMg liquid alloys at 1073 K. Interaction parameters of energy depends on temperature.

The thermodynamic properties, i.e. free energy of mixing (GM), heat of mixing (HM), entropy of mixing (SM) and activity (ai) of the component i (i , and structural property i.e. concentration fluctuations in long wave-length limit [Scc(0)] of In-Tl binary liquid alloy at a specified temperature have been investigated in the framework of quasi-lattice model on assuming the coupled effect of size ratio and entropic (or energetic) as well as enthalpic effect. These properties of In-Tl liquid alloy at 723 K have been computed theoretically by estimating the best fit value of order energy parameter (W) and size ratio () over the entire range of concentration in order to match their experimental values. The best fit value of W at 723 K has been used to determine the values of W at different temperatures with the help of temperature derivative of W which are then used for the optimization procedure in order to calculate the corresponding values of excess free energy of mixing, partial excess free energy of mixing and activity of the components involved in the alloy at different temperatures. These parameters have been used to investigate the concentration fluctuations in long wavelength limit {Scc(0)} of In-Tl binary liquid alloy at different temperatures over the entire range of concentration which have been used to predict the various other structural properties like excess stability function (EXS), diffusion coefficient ratio (Dm/Did), short range order parameter (α1) at different temperatures.BIBECHANA 15 (2018) 11-23

The thermodynamic, microscopic, surface and transport properties of Sb-Sn liquid alloy at 905K have been studied using regular solution model. In thermodynamic properties, free energy of mixing(GM) , activity(a), entropy of mixing(SM), heat of mixing (HM) have been studied. To understand structural behavior of the liquid alloys concentration fluctuations in the long wavelength limit i.e. (Scc(0)) and short range order parameter (α1) have been computed. Surface property is studied with the help of Butler’s model while transport property is computed from Moelwyn-Hughes equation. The theoretical and experimental values of thermodynamic and microscopic properties of Sb-Sn liquid alloy at 905K have been compared. In present work the value of interchange energy (w) is found to be negative suggesting that there is a tendency of unlike atoms pairing (i.e. Sb-Sn) as the nearest neighbor indicating the ordering behavior in Sb-Sn liquid alloy. The symmetric behavior of concentration fluctuations of the liquid alloy has been well explained by the model. The temperature dependence of interchange energy (w) has been found during the computation of entropy of mixing (SM) and heat of mixing (HM) of the liquid alloy.BIBECHANA 15 (2018) 1-10

We have used simple statistical theory to describe the mixing behavior of liquid Bi-In alloys in terms of energetic and structure through the study of their thermodynamic and transport properties. The structural characteristics of Bi-In melts are described by the two microscopic functions, i.e. the concentration fluctuation in long wavelength limit and the Warren-Cowley short range order parameter. The transport properties are analyzed through the diffusion coefficient ratio and viscosity. The Gibb’s free energy of mixing, enthalpy of mixing and entropy of mixing are the thermodynamic functions which are used to describe the thermodynamic behaviors. In whole analysis thermodynamic input parameter, i.e. interchange energy take important role which is temperature dependent. The computed results are in good agreement with experimental data and support a weak ordering tendency in molten Bi-In system.The Himalayan Physics Vol. 6 & 7, April 2017 (5-9)

A comparative study of the concentration dependence of surface tension and viscosity of molten In-Zn alloys at 700 K has been performed using energetics, obtained from thermodynamic analysis in the framework of self-association model. The surface tension of the alloys has been calculated from the two methods, layered structure approach and self associating mixture method, and viscosity from Moelwyn-Hughes equation and Kaptay equation. The theoretically computed results for the thermodynamic properties of the alloys are found in excellent agreement with the corresponding experimental results showing that the alloy is segregating in nature. Both surface tension and viscosity of the In-Zn alloy are found to increase with the addition of Zn atoms.The Himalayan Physics Vol. 6 & 7, April 2017 (15-19)

A theoretical assessment on thermodynamic properties and concentration fluctuations of Cu-Pb liquid alloys at a specified temperature has been made by using the fitted values for size ratio ( ) and order energy parameter (W) of the alloys in Quasi-Lattice Theory where the combined effect of size ratio, entropic and enthalpic effect is considered. The order energy parameter (W) of the alloys is temperature dependent and its value at the required temperature has been determined by using the value of order energy parameter at the given temperature and temperature derivative of order energy parameter ( ). The values of W at different temperatures have been used to determine the free energy of mixing of the alloys at different temperatures which are then used for the optimization procedure in order to calculate the corresponding values of partial excess free energy of mixing and activity of the constituents involved in the alloy at different temperatures. These parameters have been used to predict the concentration fluctuations in long wavelength limit (Scc(0)) at different temperatures in the entire range of concentration. Journal of Institute of Science and TechnologyVolume 22, Issue 1, July 2017, page: 25-33

The best fit value of order energy parameter (W) has been estimated over the entire range of concentration in Al-Sn binary liquid alloy at a specified temperature to determine the thermodynamic properties and concentration fluctuations, obtained by a theoretical formalism in which the combined effect of size ratio, entropic and enthalpic effect is considered. The values of W at different temperatures have been determined by finding the temperature derivative of W which are then used for the optimization procedure in order to determine the corresponding values of excess free energy of mixing, partial excess free energy of mixing and activity of the components involved in the alloy. These parameters have been used to calculate the concentration fluctuations in long wavelength limit {Scc(0)} at different temperatures over the entire range of concentration which predict the stability of the alloy at different temperatures.

The concentration fluctuations in long wavelength limit and thermodynamic properties, i.e. free energy of mixing, heat of mixing, entropy of mixing and activity of the components involved in the Zn-Sn binary liquid alloy at a specified temperature, have been investigated using a familiar formalism in which the combined effect of size ratio, entropic and enthalpic effect is considered. These properties of Zn-Sn liquid alloys at 750 K have been computed by estimating the best fit value of order energy parameter (W) and size ratio () in the entire range of concentration in order to match their experimental and theoretical values. This value of W has been used to determine the values of W at different temperatures with the help of temperature derivative of W which are then used for the optimization procedure in order to calculate the corresponding values of excess free energy of mixing, partial excess free energy of mixing and activity of the components involved in the alloy at different temperatures....

The mixing thermodynamic and structural properties of Zn-Cd liquid at 800K has been studied using Flory’s model. To explain the mixing properties of binary liquid alloys, size factor (ф) and ordering energy (ω) are taken into account. Thermodynamic properties like free energy of mixing (GM), activity (a), Heat of mixing (HM) and entropy of mixing (SM) and the microscopic properties like concentration fluctuation in the long wave length limit (Scc(0)) and chemical short range order parameter (α1) have been calculated. Surface property has also been studied with the help of Buttler’s model. The viscosity of the melt has been computed from Kaptay equation and BBK models. Both the viscosity and surface tension of the alloy increase with addition of zinc- component. BIBECHANA 14 (2017) 54-65

The thermodynamic properties, such as free energy of mixing, heat of mixing, activity and structural properties, such as concentration fluctuation in long wavelength limit, short-range order parameter of Pb–Hg liquid alloy at 600 K have been calculated using theoretical modelling. It has then been correlated with modified Butler model to compute the surface tension of the alloys at different temperatures. The Pb–Hg system at 600 K is found to be ordering at higher concentration of Pb.

Thermodynamic and structural properties of mixing of molten Tl–Na alloys at 673 K have been investigated using quasi-chemical model. To understand the mixing behaviour in more detail, emphasis is placed on the role of interaction energy term, and viscosity and surface tension of the alloys have also been analysed under statistical considerations. Our study shows negative deviation from the Raoultian behaviour in the properties of Tl–Na alloy thereby indicating hetero-coordination in the Tl–Na melt at 673 K in the full range of concentration. Theoretically, computed thermodynamic data at 673 K agree very well with the corresponding experimental data. The viscosities of the alloys computed from Kaptay equation show small negative deviation and those computed from Singh and Sommer’s formulation show small positive deviation from ideal values while the Budai-Benko-Kaptay equation predicts noticeable negative deviation in Na-rich end and positive deviation in Tl-rich end of the composition. The calcula...

A comparative study has been carried out to understand the concentration dependence of thermodynamic properties such as, free energy of mixing, heat of mixing, entropy of mixing, activity and microscopic properties, such as concentration fluctuation in long wavelength limit and Warren-Cowley short range order parameter of In-based three liquid alloys (In-Pb , In-Tl and In-Zn) on the basis of self-association model. The analysis reveals that self-association model successfully explains the observed properties of the liquid alloys. Positive deviation of the thermodynamic properties of the alloys from the Raoultian solution behaviour indicates that the alloys are weakly segregating in nature. The comparative assessment of the interaction energy and the microscopic properties suggests that the degree of segregation is greatest in In-Zn alloy and comparable in In-Pb and In-Tl alloys.BIBECHANA 13 (2016) 60-71

We have used simple statistical model to report the hetero-coordination of two Al- based liquid alloys, i.e. Al-Ge and Al-Fe at temperatures 2000K and 1873K respectively. Through thermodynamic functions such as free energy of mixing and ratio of activity of the component atoms of the alloys, we have reported the information on the interaction, stability and bonding strength among the constituent atoms in the alloys. At the microscopic level, concentration fluctuation in the long wavelength limit and Warren-Cowely short range order parameter help to obtain the microscopic information on structure of molten alloys. Our theoretical analysis is based on interchange or ordering energy parameter which is found to be negative and temperature dependent. Negative deviation from Raoultian behaviour is observed in the computed thermodynamic and structural parameters of the alloys. The computed results are in good agreement with experimental data. The analysis concluded that both alloys are of weakly interacting and chemically ordered system. BIBECHANA 13 (2016) 87-93

Simple statistical theory has been used to report the thermo-physical properties of mixing in liquid Cd-Zn alloys. The energetic of mixing in liquid alloys has been analyzed through the study of surface properties (surface tension, surface concentration) and transport properties (diffusivity, viscosity). Negative deviation from Raoultian behaviour has been observed in the computed mixing parameters (viscosity, surface tension) of the alloys. The computed results support a weak phase-separation tendency in molten Cd-Zn system.Journal of Institute of Science and Technology, 2014, 19(1): 14-18

We report energetic of mixing behavior of liquid Al-Ga alloys, using simple statistical theory through concentration dependence thermodynamic, structural, transport and surface properties at 1023K. The concentration dependent thermodynamic functions (free energy of mixing, enthalpy of mixing, entropy of mixing and activity coefficient of the component), structural functions (concentration fluctuation in the long wavelength limit and chemical short range order parameter), transport properties (diffusivity and viscosity) and surface properties (surface segregation and surface tension) have got special attention to show a tendency of homo-coordination of atom in the mixture. The theoretical analysis reveals that input parameter, order energy is temperature dependent and Al-Ga alloys is of weakly interacting system.Scientific World, Vol. 12, No. 12, September 2014, page 14-20

The observed asymmetry in properties of mixing of Pb-K alloys in the molten state is successfully explained on the basis of the quasi-lattice model. The thermodynamic functions such as free energy of mixing, enthalpy of mixing, entropy of mixing and chemical activity of the constituent atom of the alloys have been computed within the frame work of presented model. Most of the computed values are in good agreement with the experimental data. The pair-wise interaction energies between the species of the melt are found to depend considerably on temperature. Theoretical analysis suggests that hetero-coordination leading to the formation of complex Pb2K is likely to exist but is of weakly interacting in nature. The Himalayan Physics Vol. 5, No. 5, Nov. 2014 Page: 82-86

Thermodynamic, microscopic and surface properties of liquid Sn–Zn alloys at 750 K are reviewed in the framework of different statistical mechanical models. Flory’s model and quasi-chemical approximation (QCA) have been considered to deduce information on the concentration dependence of the thermodynamic and structural properties. The size-dependent atomic interaction has got special attention in Flory’s model, while in QCA the atomic interaction leading to the formation of like-atom clusters is assumed. Both models predict almost the same value of the interaction energy parameter in the Sn–Zn alloys, and it is found to be temperature dependent. The asymmetry in the thermodynamic properties of the alloys is explained to a great extent, and the analysis of the microscopic properties suggests that the Sn–Zn alloys are weakly segregating in nature throughout the whole range of the composition. Meanwhile, the validity of these models in describing the thermodynamic behaviour of the alloys is also examined. QCA is found to be more appropriate choice for the study of the energetics of the Sn–Zn alloys at 750 K. The comparative analysis of the surface properties under different assumptions reveals that self-associating mixture method better explains the surface behaviour in the alloys. The study indicates nonlinear variation in the concentration dependence of both the surface concentration and the surface tension of the alloys. The surface tension is found to increase with increase in Zn concentration, and the surface of the alloys is enriched with Sn atoms which segregate to the surface.

The quasi-chemical expression for weakly interacting binary alloy has been applied to obtain energy parameters and their temperature derivative for Au–Cu liquid alloy at 1550 K. These energy parameters have then been used to calculate thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing, and activity and microscopic functions, such as concentration fluctuation in long wavelength limit and Warren–Cowely short-range order parameter. The analysis reveals that the energy parameters are temperature-dependent and the Au–Cu liquid alloy at 1550 K is moderately interacting hetero-coordinating system. The observed thermodynamic properties of Au–Cu alloy in molten state have successfully been explained by assuming Au3Cu complex on the basis of the quasi-chemical formalism for weakly interacting system.

The present work reports a theoretical assessment of the composition dependence of mixing properties of liquid Na-K alloy at 384K at fixed pressure, most likely, at the atmospheric pressure. In this work we have estimated the interaction energy in the alloy at the mentioned temperature on the basis of quasi-chemical approximation for regular alloy and employed it to work out basic thermodynamic properties of mixing such as free energy of mixing, entropy of mixing and enthalpy of mixing as function of composition of the alloy. To understand the dynamic behaviour in the liquid Na-K alloy, we have carried out theoretical investigation of viscosity under consideration of Moelwyn-Hughes equation by using data for enthalpy of mixing obtained from quasi-chemical approximation. Due to scanty of experimental data on viscosity of Na-K alloy at 384K, we have performed computation of viscosity also from Kaptay equation for comparison. The calculations have shown that there is a good match between theoretically computed thermodynamic functions and the available corresponding experimental data. The sets of viscosity values obtained against composition from the two equations show deviations from the ideality and themselves are reasonably comparable to each other.DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11797BIBECHANA 12 (2015) 128-137

We report a formalism that connects thermodynamics and transport properties such as viscosity and diffusion coefficient which has been used to calculate the concentration dependence of free energy of mixing, concentration-concentration fluctuations in the long wavelength limit and concentration dependence of diffusion and viscosity in Cu-Sb and Cu-Sn binary liquid alloys at 1190K and 1400K respectively with aid of size effect and no size effect. Our calculations show that a reasonable degree of chemical order exists in both alloys system. It can be concluded that size mismatch has more effects on the transport properties of Cu-Sb hetero-coordinated system with greater size ratio than Cu-Sn hetero-coordinated system.DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11781BIBECHANA 12 (2015) 96-103

We have used simple statistical theory to report the segregating nature of In–Tl liquid alloys. The energetic of mixing in liquid alloys has been analyzed through the study of surface properties, transport properties and various thermodynamic and microscopic functions. Positive deviation from Raoultian behavior has been observed in the computed mixing thermodynamic and microscopic parameters of the alloys. The computed results are in good agreement with experimental data and support a weak phase-separation tendency in molten In–Tl system. Surface properties have also been analyzed using two different approaches which reveal that with the addition of In atoms in In–Tl alloys, surface tension of the alloy increases and Tl atoms tend to segregate at the surface.

Experimental determination of thermo-physical mixing properties of binary liquid alloys is a long and expensive task that becomes more complicated for some system which may be chemically active or radioactive or even may contain scarce components. Theoretical method, on the other hand reduces the time and efforts required, and are of great importance in predicting the properties. Now we have focused on theoretical model to study of the alloying behaviour of Cd-Bi alloys in the molten state at 773K. We have used simple statistical model to report the ordering nature of Cd-Bi liquid alloys through the study of surface properties, transport properties and various thermodynamic and microscopic functions. The knowledge of surface phenomena like surface segregation and surface tension is essential for the processing of materials and productions in the metallurgical industry. At the microscopic level, transport properties such as viscosity and diffusion coefficient help to understand about the mixing behaviour of the alloys forming molten metals. Thermodynamic properties provide information on the interaction, stability and bonding strength among the constituent atoms in the alloys. The microscopic properties are useful in obtaining the microscopic information on structure of molten alloys. Our theoretical analysis gives the negative energy parameter, which is found to be temperature dependent. Negative deviation from Raoultian behaviour is observed in the computed surface tension, thermodynamic and structural parameters of the alloys. But in case of viscosity isotherm positive deviation from ideality is observed. The computed results are in good agreement with experimental data. The analysis concluded that the alloy is of weakly interacting and heterocoordinating system. DOI: http://dx.doi.org/10.3126/bibechana.v11i0.10382 BIBECHANA 11(1) (2014) 70-78

The concentration fluctuations in long wavelength limit, Scc(0) and the Warren-Cowley short range order parameter (α1) are important microscopic functions which provide valuable information about the local arrangements of the constituent atoms in the alloy melts. In order to investigate the nature of atomic ordering in Sn-Tl alloy in the molten state at 723K, we have computed these functions using theoretical models. The models satisfactorily explain the small asymmetry observed in the experimental data of free energy of mixing of the alloy. The comparative study further reveals that the energy interaction parameters are temperature dependent and the Sn-Tl alloy is weakly interacting segregating system. DOI: http://dx.doi.org/10.3126/bibechana.v11i0.10379 BIBECHANA 11(1) (2014) 46-52

Thermodynamic, transport and surface properties of Ag–Cu liquid alloys have been investigated on the basis of a simple statistical model. The free energy of mixing, heat of mixing and entropy of mixing have been computed to understand the thermodynamic properties of Ag–Cu alloys in liquid state at 1,423 K. The concentration–concentration fluctuations in the long wavelength limit and the chemical short range order parameter have been determined to comprehend the microscopic and structural information of the alloy. The viscosity and surface tension of the alloy have been evaluated to analyze the transport and surface properties. The theoretical analysis reveals that the energy parameter is temperature dependent, and that Ag–Cu liquid alloy is a weakly interacting-phase separating system.

The segregating nature of Cd–Pb liquid alloys has been reported using simple statistical theory of mixing. The energetics of mixing in liquid binary alloys has been analysed through the study of surface properties (surface tension and surface concentration), transport properties (viscosity and chemical diffusion) and various thermodynamic and structural functions. Positive deviation from Raoultian behaviour has been observed in the computed mixing parameters of the alloys. Our results are in good agreement with experimental data and support a weak demixing tendency in Cd–Pb liquid alloys.

The deviation from ideal mixture behavior and concentration dependent symmetry in the microscopic and surface properties of K-Na liquid alloy is investigated within a simple statistical model. The concentration dependent of microscopic functions(concentration fluctuation in the long wavelength limit, Warren-Cowley short range order parameter) and surface properties(surface concentration and surface tension) has got special attention to show a tendency of like atom pairing in the mixture. The theoretical analysis reveals that energy parameter is temperature dependent, K-Na alloys is of weakly interacting system and K-atoms segregates on the surface of K-Na liquid alloys at bulk concentration of Na.The Himalayan Physics Vol. 4, No. 4, 2013 Page: 40-45 Uploaded date: 12/23/2013

Thermodynamic, transport and surface properties of liquid In–Pb alloys have been investigated using the simple statistical model. The free energy of mixing, heat of mixing, entropy of mixing and activity of components of liquid alloys In–Pb at 637 K have been computed. The microscopic function, concentration–concentration fluctuations in long wavelength limit have been studied to investigate the stability and microscopic structural information about liquid alloys and chemical short range order parameter has been calculated to quantify the degree of atomic order. The same energy parameters have been used to compute diffusion coefficients ratio, viscosity, surface tension and surface concentration of liquid In–Pb alloys. The study reveals that liquid In–Pb alloy is weakly interacting and phase separating system.

Quasi-chemical approximation has been used to study the mixing behaviour of liquid aluminium-gallium binary alloys by computing thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing, activity and microscopic functions, such as concentration fluctuation in long wavelength limit (Scc(0)), Warren-Cowley short range order parameter (

The mixing behaviour of liquid cadmium–indium alloys has been analysed on the basis of quasi-chemical approximation by computing thermodynamic parameters, such as free energy of mixing (G M), entropy of mixing (S M), heat of mixing (H M) and chemical activities (a i) and structural functions, such as concentration fluctuation in the long wavelength limit (S cc(0)), the Warren–Cowley short-range order parameter (α 1) and the ratio of diffusion coefficients (D m/D id) of the alloys at 800 K. The analysis suggests that there is a tendency of like atom pairing (Cd–Cd, In–In) in Cd–In alloy over entire concentrations and ordering energy is found to be temperature dependent. Cd–In alloy at 800 K in the molten state is slightly segregating in nature.

The mixing behaviour of cadmium–zinc binary liquid alloys have been examined by computing thermodynamic properties, such as free energy of mixing (GM), heat of mixing (HM), entropy of mixing (SM), activity (ai) and microscopic functions, such as concentration fluctuations in long wavelength limit (Scc(0)), Warren–Cowley short range order parameter (α1) and ratio of diffusion coefficients of the alloys at 800 K using statistical model in the framework of quasi-chemical approximation. Surface properties have also been analysed using four different approaches. The theoretical study reveals that the ordering energy parameters are temperature dependent and all the observed thermodynamic parameters are in reasonable agreement with the observed values. The Cd–Zn liquid alloys at 800 K represent a segregating system with segregation of Cd-atoms at the surface. The values of surface tension obtained from different approaches have been found to be comparable with each other.

The quasi-lattice model based on pairwise interactions has been used to study the large deviation from the ideal mixture and the concentration dependent asymmetry in the thermodynamic properties of Mg-Bi liquid alloy. This has been utilised to extract microscopic information such as concentration-concentration structure factor in long wavelength limit [Scc(o)] and warren-cowley short range order parameter 1 of Mg-Bi liquid alloy at 975K. The analysis suggests that heterocoordination leading to the formation of complex Mg3Bi2 is likely to exist in the melt, and is of strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is chemically more ordered in Mg-rich region of the phase diagram. The alloy behaves like a segregating system in Bi-rich region. Copyright © 2013 VBRI press.

The deviation from ideal mixture behavior and concentration dependent symmetry in thermodynamic and structural properties of K-Na liquid alloy is investigated within a simple statistical model. The concentration dependence of the free energy of mixing, heat of mixing, entropy of mixing, concentration fluctuation in the long wavelength limit, Warren-Cowley short range order parameter, ratio of diffusion coefficients of Potassium-sodium alloy at 384 K and activity of the components has got special attention to show a tendency of like atom pairing in the mixture. DOI: http://dx.doi.org/10.3126/bibechana.v9i0.7187 BIBECHANA 9 (2013) 130-135

We have studied the microscopic structure such as, concentration fluctuation in long wavelength limit (SCC(0)), Warren–Cowely short range order parameter (α 1), ratio of mutual and intrinsic diffusion coefficients (D M/D id) of molten Al–Si alloy at 1700 K using a statistical model of complex formation on the basis of quasi-lattice theory for weakly interacting systems. The approach used in this article reveals that molten Al–Si alloy at 1700 K is a weakly interacting heterocoordinating system and the alloy is more ordered in the Al-rich end.

The quasi-chemical expression for weakly interacting binary alloy has been applied to obtain energy parameters and their temperature derivatives for Na–K liquid alloy at 384 K. These energy parameters have then been used to calculate thermodynamic functions, such as free energy of mixing, heat of mixing, entropy of mixing and microscopic functions, such as concentration fluctuation in long wavelength limit, Warren–Cowley short-range order parameter, ratio of mutual and self-diffusion coefficients. The analysis reveals that the energy parameters are temperature dependent and the Na–K liquid alloy at 384 K is a weakly interacting homocoordination system. The observed thermodynamic properties of Na–K alloy in molten state have successfully been explained by assuming Na2K complex on the basis of the quasi-chemical formalism for a weakly interacting system.

Flory’s model has been used to study the mixing properties of Al–Mg liquid alloy at 1,073 K. The values of different thermodynamic parameters obtained from this model are compared with corresponding experimental values. Most of the computed values are found to be in good agreement with the observed values.

The thermodynamic properties such as, free energy of mixing ( G M ), heat of mixing ( H M ), entropy of mixing ( S M ) and microscopic properties such as, concentration fluctuation in long wavelength limit ( S CC (0)), Warren–Cowely short range ordering parameter (α 1 ), ratio of mutual and intrinsic diffusion coefficients ( D M / D id ) of two Cd-based liquid alloys have been studied by using two different models. The properties of Cd–Hg liquid alloy at 600 K have been studied on the basis of regular solution model, and the properties of Cd–Na liquid alloy at 673 K have been studied on the basis of quasi-chemical expression for weakly interacting system.

The alloying behaviour of Na–Sn liquid alloys at 773K has been studied by using regular associated solution model. This model has been utilized to determine the complex concentration in a regular associated solution of Na and Sn. We have then used the complex concentration to calculate the free energy of mixing (GM), enthalpy of mixing (HM), entropy of mixing (SM), concentration fluctuations in long wavelength limit (SCC(0)), the Warren Crowley short-range parameter (α1) and ratio of mutual and intrinsic diffusion coefficients (DM/Did). The analysis suggests that heterocoordination leading to the formation of complex Na3Sn is likely to exist in the liquid and is of a strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloys are more ordered towards intermediate region.

The mixing behaviour of two Na-based alloys has been studied in their liquid states. We have calculated free energy of mixing, activity, concentration fluctuation in long-wavelength limit and chemical short-range ordering parameter for the InNa alloy at 713 K and for the NaPb alloy at 700 K. This analysis shows that both the alloys show heterocoordinating interaction systems in liquid state.

The quasi-lattice model has been used to study the concentration dependant thermodynamic properties and microscopic structure of Fe–Si alloys in molten state. We have determined the free energy of mixing, excess entropy of mixing, the concentration–concentration structure factor in long wavelength limit [ S CC (0)] and the Warren–Cowley short range order parameter ( α 1 ) of Fe–Si liquid alloy at 1873 K. The observed asymmetry in the properties of mixing of Fe–Si alloy in molten state is successfully explained on the basis of the quasi-lattice model. The analysis suggests that the Fe 2 Si complexes are most likely to exist in the liquid state and are strongly interacting in nature. The theoretical analysis suggests that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered towards Fe rich region.

The concentration dependent asymmetry in mixing properties of LiMg liquid alloys at 1000 K has been investigated on the basis of regular associated solution model. The analysis suggests that heterocoordination leading to the formation of chemical complex Li2Mg is likely to exist in the melt.

We have studied the thermodynamic properties and microscopic structures of HgNa liquid alloy at 673 K on the basis of regular associated solution model. The concentrations of ApB type complex in a regular associated solution of Hg and Na have been determined. We have then used the concentration of complex to calculate the free energy of mixing, enthalpy of mixing, entropy of mixing, activity, concentration fluctuations in long wavelength limit S CC (0) and the Warren–Cowley short-range parameter α 1 . The analysis suggests that heterocoordination leading to the formation of complex Hg 4 Na is likely to exist in the liquid and is of a strongly interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend considerably on temperature and the alloy is more ordered towards Hg-rich region.

Binding of the vitamin folic acid with bovine serum albumin (BSA) has been studied using isothermal titration calorimetry (ITC) in combination with fluorescence and circular dichroism spectroscopies. The thermodynamic parameters of binding have been evaluated as a function of temperature, ionic strength, in the presence of nonionic surfactants triton X-100, tetrabutylammonium bromide, and sucrose. The values of the van't Hoff enthalpy calculated from the temperature dependence of the binding constant agree with the calorimetric enthalpies indicating that the binding of folic acid to the BSA is a two state process without involving intermediates. These observations are supported by the intrinsic fluorescence and circular dichroism spectroscopic measurements. With increase in the ionic strength, reduction in the binding affinity of folic acid to BSA is observed suggesting predominance of electrostatic interactions in the binding. The contribution of hydrophobic interactions in the binding is also demonstrated by decrease in the binding affinity in the presence of tetrabutylammonium bromide (TBAB). The value of binding affinity in the presence of sucrose indicates that hydrogen bonding also plays a significant contribution in the complexation process. The calorimetric and spectroscopic results provide quantitative information on the binding of folic acid to BSA and suggest that the binding is dominated by electrostatic interactions with contribution from hydrogen bonding. (C) 2011 Elsevier Ltd. All rights reserved.

The thermodynamic and microscopic structure of MgTl liquid alloy at 923 K has been studied by using regular associated solution model. The free energy of mixing, heat of mixing, entropy of mixing, activity, concentration fluctuations in long-wavelength limit S CC (0) and the Warren–Cowley short-range parameter α 1 have been determined. The analysis suggests that this alloy is of a moderately interacting nature. The theoretical analysis reveals that the pairwise interaction energies between the species depend on temperature and there is a tendency of unlike atoms pairing (Mg–Tl) in liquid MgTl alloys at all concentration. The observed asymmetry in the properties of mixing of MgTl alloy in molten state is successfully explained by assuming MgTl complex on the basis of regular associated solution model.

The mixing properties of CuPd alloy in molten state at 1350 K have been studied by assuming strong interaction between Cu and Pd atoms. Regular associated solution model has been used for the study. The asymmetry in integral excess free energy of mixing, heat of mixing and entropy of mixing has been well explained.