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Featured researches published by V. B. Gohel.


International Journal of Modern Physics B | 2005

THERMODYNAMIC PROPERTIES OF 4f- AND 5f-SHELL METALS AT FINITE TEMPERATURES: MEAN-FIELD POTENTIAL APPROACH IN CONJUNCTION WITH LOCAL PSEUDOPOTENTIAL

N. K. Bhatt; P. R. Vyas; A. R. Jani; V. B. Gohel

The thermodynamic properties of 4f- and 5f-shell metals have been studied at high temperatures using mean-field potential approach. The MFP seen by the lattice ion is constructed in terms of the total energy-volume relation using local pseudopotentials due to Pandya et al. [Physica B 307, 138 (2001)]. We have calculated static compression, shock-wave compression, volume thermal expansion, isothermal and adiabatic bulk moduli (BT and BS), specific heats (CV and CP), thermodynamic Gruneisen parameter (γth), anharmonic contribution to the specific heat and temperature along shock Hugoniot for 4f (γ-Ce)- and 5f (fcc-Th)-shell metals. The results are well compared with the other theoretical and experimental findings, which ensure the use of pseudopotentials for studying thermodynamic properties at higher temperatures in case of lanthanides and actinides.


Phase Transitions | 2017

The study of anharmonic properties and s-p-d hybridization in barium at extreme environment

Priyank Kumar; N. K. Bhatt; P. R. Vyas; V. B. Gohel

ABSTRACT Theory of pseudopotential has been used in the present study to carry out computation of various thermodynamic parameters of barium. The role of anharmonic effect due to vibrations of lattice ions has been accounted by coupling local pseudopotential with mean field potential which has been computed using second-order perturbation theory. Contribution due to thermally excited electrons has been accounted by Mermin functional. The excellent agreement of presently computed pressure with experimental result has also been observed at which body centered cubic to hexagonal close packed structure phase transition occurs. Such success leads to conclude that the s-p-d hybridization and anharmonic effects are included properly in the presently used conjunction scheme with additional advantage of its computational simplicity.


International Journal of Modern Physics B | 2017

Mean-field potential approach for thermodynamic properties of lanthanide: Europium as a prototype

Priyank Kumar; N. K. Bhatt; P. R. Vyas; V. B. Gohel

In the present paper, a simple conjunction scheme [mean-field potential (MFP) + local pseudopotential] is used to study the thermodynamic properties of divalent lanthanide europium (Eu) at extreme environment. Present study has been carried out due to the fact that divalent nature of Eu arises because of stable half-filled 4f-shell at ambient condition, which has great influence on the thermodynamic properties at extreme environment. Due to such electronic structure, it is different from remaining lanthanides having incomplete 4f-shell. The presently computed results of thermodynamic properties of Eu are in good agreement with the experimental results. Looking to such success, it seems that the concept of MFP approach is successful to account contribution due to nuclear motion to the total Helmholtz free energy at finite temperatures and pressure-induced inter-band transfer of electrons for condensed state of matter. The local pseudopotential is used to evaluate cold energy and hence MFP accounts the s–p–d–f hybridization properly. Looking to the reliability and transferability along with its computational and conceptual simplicity, we would like to extend the present scheme for the study of thermodynamic properties of remaining lanthanides and actinides at extreme environment.


Chinese Physics B | 2016

Thermophysical properties of iridium at finite temperature

Priyank Kumar; N. K. Bhatt; P. R. Vyas; V. B. Gohel

The bulk properties of materials in an extreme environment such as high temperature and high pressure can be understood by studying anharmonic effects due to the vibration of lattice ions and thermally excited electrons. In this spirit, in the present paper, anharmonic effects are studied by using the recently proposed mean-field potential (MFP) approach and Mermin functional which arise due to the vibration of lattice ions and thermally excited electrons, respectively. The MFP experienced by a wanderer atom in the presence of surrounding atoms is constructed in terms of cold energy using the local form of the pseudopotential. We have calculated the temperature variation of several thermophysical properties in an extreme environment up to melting temperature. The results of our calculations are in excellent agreement with the experimental findings as well as the theoretical results obtained by using first principle methods. We conclude that presently used conjunction scheme (MFP+pseudopotential) is simple computationally, transparent physically, and accurate in the sense that the results generated are comparable and sometimes better than the results obtained by first principle methods. Local pseudopotential used is transferable to extreme environment without adjusting its parameters.


ADVANCED MATERIALS AND RADIATION PHYSICS (AMRP-2015): 4th National Conference on Advanced Materials and Radiation Physics | 2015

Theoretical study of pressure dependence of transition temperature of In and Pb

Priyank Kumar; N. K. Bhatt; P. R. Vyas; V. B. Gohel

Recently proposed structured local pseudopotential (PP) by Fiolhais et al. has been successfully used to compute superconducting state parameters (SSP): electron-phonon coupling strength (λ), Coulomb pseudopotential (μ*), critical temperature (Tc), effective interaction strength (N0V), isotopic effect parameter (α) and their pressure dependence of non-transition metals In and Pb as a test case. Pressure dependence of the Debye temperature has been computed by Gruneisen model. Present results are in good agreement with experimental and other theoretical results. Present study has been further extended to estimate volume (critical volume) at which λ=μ*, where Tc and N0V becomes zero. The presently used model is found to be transferable at the extreme environment without any adjustment of parameters further alongwith its simplicity and predictivity.


Solid State Phenomena | 2013

Thermal Expansion of Some Fcc Transition Metals

Priyank Kumar; N. K. Bhatt; P. R. Vyas; A. R. Jani; V. B. Gohel

Volume thermal expansion of some fcc transition metals have been studied using improved lattice dynamical model. In this approach, the contribution of s like electron is calculated in 2nd order perturbation theory for the local model pseudopotential (Heine - Abrenkov) while that of the d electrons is taken into account by introduction of repulsive potential. The present study confirms that the use of improved model to study such anharmonic property yields satisfactory results. Looking to the success of present study, the present lattice mechanical model may be used to study thermophysical properties in high temperature and high pressure regions.


PROCEEDING OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN APPLIED PHYSICS AND MATERIAL SCIENCE: RAM 2013 | 2013

Thermal expansion of noble metals using improved lattice dynamical model

Priyank Kumar; N. K. Bhatt; P. R. Vyas; V. B. Gohel

Isothermal bulk modulus and volume thermal expansion for noble metals have been studied on the basis of improved lattice dynamical model proposed by Pandya et al [Physica B 307, 138-149 (2001)]. The present study shows that for all three noble metals the approach gives satisfactory results, when they are compared with experimental findings. The present study thus confirms the use of improved model to study anharmonic property, and can be extended to study temperature dependent properties in high temperature range.


SOLID STATE PHYSICS, PROCEEDINGS OF THE 55TH DAE SOLID STATE PHYSICS SYMPOSIUM 2010 | 2011

The Resistivity of Liquid Less‐Simple Metals with Finite Mean Free Path using Effective Local Pseudopotentials

M. B. Pathak; P. R. Vyas; N. K. Bhatt; A. R. Jani; V. B. Gohel

The resistivity of liquid less‐simple metals is calculated using Ziman’s theory. The effective electron‐ion interaction pseudopotential constructed from energy‐wave number characteristics, which is obtained through first principles, has been used in the present study. The self‐consistent electrical resistivity is evaluated by considering blurring of the Fermi surface due to finite mean free path of electrons. Our results are well compared with experiments and other theoretical findings. It is pointed out that the presently generated local pseudopotentials not only suffice for electrical properties, but has an additional advantage of making calculations simple.


Journal of Physics and Chemistry of Solids | 2005

Thermodynamic properties of the alkali metals at high temperatures and high pressures using mean-field potential model

N.K. Bhatt; P.R. Vyas; A. R. Jani; V. B. Gohel


Physica B-condensed Matter | 2005

Thermodynamic properties of lead at high temperatures and high pressures—mean-field potential approach

N.K. Bhatt; A. R. Jani; P.R. Vyas; V. B. Gohel

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A. R. Jani

Sardar Patel University

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