Vamshi Prasad - Academia.edu (original) (raw)

Papers by Vamshi Prasad

Materials Today: Proceedings, Apr 1, 2023

Materials Today: Proceedings

Physica B: Condensed Matter, 2021

Abstract Complex permittivity of the binary mixtures of N-Methyl-2-Pyrrolidone (NMP) with Ethanol... more Abstract Complex permittivity of the binary mixtures of N-Methyl-2-Pyrrolidone (NMP) with Ethanol (ETH) has been studied in the microwave frequency range at various temperatures. The binary liquid system NMP-ETH is selected to interpret the effect of carbonyl (-C O) group of NMP and hydroxyl group (-OH) of ETH on the volumetric, thermal and dielectric properties. The dipole moment (μ) and relaxation time (τ) is evaluated from Higasi's method and Havriliak-Negami equation. The excess molar volume (VmE), excess permittivity (eE), excess refractive index (nDE), excess inverse relaxation time (1/τ)E are fitted with the Redlich-Kister equation. The results obtained from Polarizable Continuum Model (PCM) and Integral Equation Formalism Polarizable Continuum Model (IEFPCM) solvation theories using DFT methods are correlated with the experimentally determined parameters. The molecular association and chemical stability of the system is interpreted in terms of single-point energy, HOMO-LUMO calculations. The existence of a hydrogen bond within the NMP-ETH system is confirmed from the FT-IR, UV–Vis's spectra.

Journal of Molecular Liquids, 2019

A study on the dielectric properties of various molar concentration levels of aqueous L-glutamine... more A study on the dielectric properties of various molar concentration levels of aqueous L-glutamine, ethanol mixtures at microwave frequency region (0.02 b ν/GHz b 20) is carried out in the temperature range of 298 K to 323 K. Dielectric parameters such as dielectric permittivity, dielectric loss of different molar concentrations of L-glutamine in water, ethanol medium are evaluated. It is noticed that the real and imaginary part of dielectric permittivity increases with increase in molar concentration levels of L-glutamine in water and ethanol medium and decreases with increase in temperature. From these parameters, average relaxation time (τ), excessive inverse relaxation time (1/τ) E , excessive dielectric permittivity (ε E) are determined and their behavior is analyzed in terms of the distribution of hydrogen bond network in the liquid medium. The theoretical dipole moments of Lglutamine in both aqueous and ethanol medium are determined by using DFT-B3LYP method with different solvation models. Mean molecular polarizability (α M) of the system is calculated from the Lippincott δ function potential model and compared with the Lefevre method. The activation entropy (ΔS*), activation enthalpy (ΔH*), Helmholtz energy (ΔF E) parameters have also been evaluated and the results are correlated.

Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2019

The complex dielectric permittivity of L-alanine in aqueous medium at different concentrations an... more The complex dielectric permittivity of L-alanine in aqueous medium at different concentrations and different temperatures were measured in the microwave (0.02< ν/GHz <20) frequency region by using open-ended coaxial probe technique. From the reflection coefficient and impedance data, the real and imaginary part of the dielectric permittivity values is determined. It is observed that there is a decrease in the real part of the dielectric permittivity up to certain frequency and an increase in the imaginary part of the dielectric permittivity with increase in the molar concentration of L-alanine in water medium. Based on the experimental data the average relaxation time values are calculated and its behavior is analyzed in terms of bound water and free water molecules. The theoretical dipole moment of L-alanine is calculated at gaseous state as well as in aqueous medium by using PCM and IEFPCM model at HF, DFT/B3LYP and MP2 calculations using 6-311G* basis set. Analysis between experimentally determined parameters and computed dipole moments were discussed. The mean molecular polarizability is calculated from the Lippincott δ function potential model and compared with the Le Fèvre method of polarizability values.

Journal of Molecular Structure, 2021

Abstract In this paper, we report the dielectric permittivity of the Glycerol (Gly) with N-Methyl... more Abstract In this paper, we report the dielectric permittivity of the Glycerol (Gly) with N-Methyl-2-Pyrrolidone (NMP) binary mixtures in the microwave frequency region at different temperatures. The dipole moments of Gly, NMP and their equimolar binary mixtures are calculated by using Higasi's method in the temperature range 298.15K-323.15K. The dielectric relaxation spectra of the binary mixtures are calculated using Cole-Cole and Cole-Davidson equation and shows an unsymmetrical relaxation behaviour. The excess parameters of volume, permittivity, refractive index, polarization and relaxation times are fitted with Redlich-Kister polynomial equation. The molecular association and their hydrogen bond interactions between the components in the mixture are discussed in terms of Kirkwood correlation geff factor and excess Helmholtz energy ( Δ F E ) equation. The mean molecular polarizability (αM) of the individual and their binary mixture are calculated using Lippincott δ- function potential model and compared with the LeFevre method of polarizability values. The enthalpy of activation ΔH*, entropy of activation ΔS* and Gibbs free energy of activation ΔG* are also evaluated and the results are discussed in terms of the orientation of the dipoles. The presence of hydrogen bonding between Gly and NMP is confirmed from the FT-IR spectra.