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Papers by Author: Amitava Ghorai

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A Review of Diffusion and Interfacial Reactions in Sandwich Thin-Film Couples

Authors: Amitava Ghorai, D. Roy

Abstract: In this paper different techniques for sandwich thin film production, characterization and interfacial reactions have been reviewed in order to understand the kinetic behaviour in the above systems. The contact and composite resistance measurements are the indirect methods for this purpose, while X-ray diffraction studies (XRD), Transmission electron microscopy (TEM), Scanning electron microscopy (SEM), Rutherford backscattering (RBS), Auger electron spectroscopy (AES), secondary ion mass spectrometry (SIMS), ion sputtering spectrometry (ISS), X-ray photoelectron spectroscopy (XPS) which is also referred to as electron spectroscopy for chemical analysis (ESCA) and atomic force microscopy (AFM) are some of the direct methods. Trends indicate that interfacial reactions start at room temperature.

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Calculation of Parameter of Ashcroft’s Potential Using Vacancy Formation Energy for some BCC Metals: Li, Na, K, Rb, Cs, Ba

Authors: Amitava Ghorai, T. Choudhury, Arjun Das, R. Dey, S. Ganguly

Abstract: The graphs for variation of vacancy formation energy ( ) with r_c of Ashcroft's empty core model potential for different exchange and correlation functions are shown for six bcc metals, viz. Li, Na, K, Rb, Cs and Ba. Fitted value of for Li, Na, K, Rb, Cs and Ba are respectively 1.343, 1.694, 2.205, 2.384, 2.962 and 2.337 atomic unit (AU).

A Review of some Theoretical Models for Point Defect Calculations

Authors: Amitava Ghorai

Abstract: A Brief Sketch of Different Models for the Calculation of Defect Parameters in Metals and Alloys, Comparison of Data and Limitations Has Been Reviewed here; Especially Relaxations due to a Vacancy Type of Point Defect, its Formation, Migration, Activation Energies and Related other Parameters Based upon the Present Experimental Status. the Models Reviewed Are the Bond Model, Continuum Model, Semi-Discrete Model, Jellium Model, Thermodynamic Model, Lattice Statics Model, Atomistic Continuum Model and Pseudopotential Model. the Main Thrust Concerns the Last Model. the Taylor, Vashishta and Singwi, Harrison, Kleinmann and King and Kutler Form of Exchange and Correlation Function Are Almost Similar, Give Moderate Results and May Be Trusted for Better Results.

Study of the Dielectric, Magnetic and Resistive Properties of Various Substances

Authors: Amitava Ghorai, Rabindranath Singh, Mrinal Kanti Hota, Dhananjay Bej

Abstract: The value of dielectric constant of paraffin wax doped with different concentrations of lamp black carbon decreases with the increase in the concentration of lamp black carbon in it. It is a case of loss of dielectric property and gain in conducting property and the specimen behaves as a random binary mixture of conductors and insulators, more specifically, a random network of resistors and capacitors. Anderson Bridge is used to investigate the magnetic permeability and susceptibility of different media inside a solenoid. The resistive property of manganin wire is studied using Kelvin double Bridge.

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Formulation of Impurity-Vacancy Pair Formation Energy in Fast Diffusion

Authors: Amitava Ghorai

Abstract: In fast diffusion, the impurity diffusion coefficient is much greater than the self-diffusion coefficient. The pair mechanism is here considered to explain fast diffusion. Formulations for the formation of the pair are based upon pseudopotential theory.

Exploration of Parameters of Ashcroft’s Potential Using Monovacancy Formation Energy and Different Exchange and Correlation Functions for some Trivalent FCC Metals

Authors: Amitava Ghorai

Abstract: A pseudopotential approach has been used to study the variation of the vacancy formation energy as a function of the parameter of Ashcroft's empty core model potential (AECMP) and nine different exchange and correlation functions (ECF) for some trivalent fcc metals, viz. Al, La, Sc, γ-Ce, Pr and Yb. The criterion used is that should be greater than the Bohr radius ( ). There is a systematic increase in the fitted value of in going from one ECF to another, as follows: KK < Sham < GV < Kle < Harr < VS < Tay < Hub < MD and it is difficult to assign a particular value of for all ECFs for a particular trivalent fcc metal. The inherent simplicity of AECMP makes it difficult to have a universal parameter for all types of atomic property calculations.

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A Study of the Variation of Monovacancy Formation Energy with the Parameter of Ashcroft's Potential and Different Exchange and Correlation Functions for Some Group-IIa and Group-VIII FCC Metals in the Active Divalent State

Authors: Amitava Ghorai

Abstract: Graphs of monovacancy formation energy ( ) versus the parameter, , of Ashcroft's empty-core model potential (AECMP) and nine different exchange and correlation functions (ECF) are shown for two different group-IIa divalent fcc metals (Ca and Sr) and seven group-VIII divalent fcc metals in an active valence state (γ-Fe, β-Co, Rh, Ir, Ni, Pd and Pt). The criterion used is that is greater than the Bohr radius. There is a systematic increase and decrease in the fitted value of , and the calculated value of , respectively, in going from one ECF to other, as follows: Sham

Formation of Point Defects in Dilute FCC Alloys

Authors: Amitava Ghorai

Abstract: Using pseudopotential approach, vacancy formation energy , different non-split interstitial formation energies and binding energy for the vacancy-impurity pair and that for interstitial impurity over host have been calculated in some cubic fcc metal systems, viz. copper, silver, gold and lead using Ashcroft's potential and Taylor's exchange and correlation function with standard (AT) and fitted to (ATF) and also Heine-Abarenkov’s model potential and same exchange and correlations (HAT). It is difficult to have a universal value for all types of atomic property calculations. The results show that ATF and HAT combinations are better in comparison to AT. Also, the substitutional impurity adjacent to a vacancy is found to be more loosely bound than the interstitial impurity in fcc metals.

Dependence of Mono-Vacancy Formation Energy on the Parameter of Ashcroft's Potential

Authors: Amitava Ghorai

Abstract: We show the calculation of the monovacancy formation energy ( v FH E1 ) for three different group-I monovalent fcc metals (Cu, Ag and Au) and two group-IV tetravalent fcc metals (Pb and Th) use a pseudopotential approach. Ashcroft's empty core model potential (AECMP) and nine different exchange and correlation functions (ECF) are used. The variation of v FH E1 with the parameter c r of AECMP for different ECF shows variations with the metals, and c r is observed to be greater than Bohr radius.