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1

Structural Properties of Some Alkali Metal Hydrides at High Temperature and Pressure

100%

Thakre V., Singh S.

Acta Physica Polonica A

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2018

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vol. 133

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issue 1

186-193

EN

In this paper we have developed a realistic interaction potential model to study the high pressure phase transition of ionic alkali-metal compounds KH and NaH, having B₁ structure at room temperature. We have theoretically investigated phase transition pressures and volume collapses of KH and NaH at high temperatures, and found results well suited with available experimental data. The elastic constants and their pressure derivatives are reported first time. The thermodynamical properties of B₁ phase of KH and NaH are also predicted. The inclusion of temperature effect in TBIP makes the present model realistic and suitable for theoretical high-pressure studies.

2

High Pressure Phase Transition and Allied Behavior οf Samarium Compounds

81%

Singh M., Gour A., Singh S.

Acta Physica Polonica A

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2013

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vol. 123

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issue 4

709-713

EN

A theoretical study of the phase transition of samarium monochalcogenides using three-body interaction potential model is carried out at high pressure. The three-body interaction potential includes long range Coulombic, three-body interaction forces and short range overlap repulsive forces operative up to next nearest neighbor ions. We have investigated phase transition pressures, volume collapses, elastic behavior, stability criteria and various thermo physical properties at various high pressure. The results found are well suited with available experimental data. In this paper third order elastic constants are also reported for the first time which helps in understanding the nature of interionic forces in ionic solids which paved the experimentalist to work in specific direction.

3

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

81%

Singh S., Chauhan R., Gour A.

Acta Physica Polonica A

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2011

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vol. 120

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issue 6

1021-1025

EN

We have carried out high pressure theoretical structural studies of yttrium nitride to examine the phase transition phenomena from the NaCl structure to CsCl structure by using a three-body potential model. The phase transition pressure (140 GPa) predicted by this approach is close to the phase transition pressure, predicted by others (138 GPa). Yttrium nitride is a novel and less explored material. Under high pressure yttrium nitride goes through a sudden collapse in volume showing the first order phase transition. To understand the effect of pressure we studied bulk properties, elastic constants and their combination. The pressure volume equation of state provides meaningful signatures of physical and chemical phenomena under high pressure. Moreover we have successfully checked the stability criterion for this compound.

4

Modulation of radiation-induced biochemical changes in cerebrum of Swiss albino mice by Grewia asiatica

81%

Sisodia R., Ahaskar M., Sharma K. V., Singh S.

Acta Neurobiologiae Experimentalis

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2008

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vol. 68

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issue 1

32-38

EN

The present study evaluates the possible radioprotective effect of Grewia asiatica fruit (rich in anthocyanin, carotenes, vitamin C, etc.) pulp extract (GAE) on cerebrum of Swiss albino mice exposed to 5 Gy gamma radiation. For this, healthy mice from an inbred colony were divided into four groups: (1) Control (vehicle treated), (2) GAE treated ? mice in this group were orally supplemented with GAE (700 mg/kg. b.w. /day) once daily for fifteen consecutive days, (3) Vehicle treated irradiated mice, and (4) GAE + Irradiated ? Mice in this group received distilled water orally equivalent to GAE (700 mg/kg. b.w./day) for fifteen days consecutively. Mice were sacrificed at various intervals viz. 1?30 days. Radiation-induced augmentation in the levels of lipid peroxidation of mice cerebrum was significantly ameliorated by GAE pretreatment. Radiation-induced depletion in the level of glutathione and protein was prevented significantly by GAE administration.

5

Modelling and Experimental Characterization of Processing Parameters in Vertical Twin Roll Casting of Aluminium Alloy A356

72%

Dhindaw B., Singh S., Mandal A., Pandey A., Dhindaw B., Singh S., Mandal A., Pandey A.

Archives of Foundry Engineering

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2020

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vol. 20

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issue 4

6

Volumetric, Optical, Acoustical and Viscometric Study of Molecular Association in Binary Mixtures of Butylamine with 1-Butanol and Tert-Butanol

71%

Singh S., Parveen S., Shukla D., Gupta M., Shukla J.

Acta Physica Polonica A

|

2007

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vol. 111

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issue 6

847-858

EN

Density (ρ), refractive index (n), ultrasonic velocity (u), and viscosity (η) were measured for the binary mixtures formed by butylamine with 1-butanol and tert-butanol at temperatures 293, 303, and 313 K over the entire composition range. Excess molar volume V_m^E, molar refraction deviation ΔR_m, deviation in ultrasonic velocity Δu, viscosity deviation Δη, and excess Gibb's free energy of activation for viscous flow ΔG^{*E} were derived from the experimental data and the computed results were fitted to the Redlich-Kister polynomial equation. The values of V_m^E, ΔR_m, Δu, Δη, and ΔG^{*E} were plotted against the mole fraction of butylamine. The observed positive and negative values of excess parameters for both the mixtures were explained on the basis of intermolecular interactions present in these mixtures. The higher negative values of V_m^E and ΔR_m and positive values of Δu, Δη, and ΔG^{*E} for butylamine + 1-butanol mixture suggest that specific interactions are taking place in butylamine + 1-butanol mixture, while weak dipole-dipole induced forces and dispersive forces seem to be responsible for butylamine + tert-butanol mixture. Furthermore, different empirical relations were used to correlate the binary refractive indices. An excellent agreement was found between experimental and theoretical values.

7

Effect of van Hove Singularity on T_c in Rb doped C_{60}

61%

Agrawal B., Agrawal S., Yadav P., Srivastava P., Srivastava R., Singh S.

Acta Physica Polonica A

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2003

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vol. 103

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issue 5

477-482

EN

In the present study we investigate the role of van Hove singularity on the optimization of T_c in Rb doped fullerenes C_{60} Rb_3. A first principles self-consistent full potential linear muffin-tin orbital method using density functional theory in local density approximation was employed. The doped Rb atoms are of two types occupying the tetrahedral and interstitial positions in the fcc lattice. The added Rb atoms fill the t_{1u} band of the undoped fullerenes C_{60} up to half which makes C_{60}Rb_3 conducting. Saddle points leading to van Hove singularities are observed in the neighbourhood of the symmetry point L. The shifting of the van Hove singularity with the volume of the lattice is investigated. We observe a saddle point just at the Fermi level for a lattice constant of 14.435Å. The highest value of T_c should thus be observed at the above lattice constant. This result is in excellent agreement with the observed high value of T_c measured in C_{60}Rb_3 for a lattice constant of 14.435Å.

8

Molecular Interaction Study of Binary Mixtures of THF with Methanol and o-Cresol - an Optical and Ultrasonic Study

61%

Parveen S., Singh S., Shukla D., Singh K., Gupta M., Shukla J.

Acta Physica Polonica A

|

2009

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vol. 116

|

issue 6

1011-1017

EN

The refractive indices, densities and ultrasonic velocities of binary liquid mixtures of tetrahydrofuran (THF) with methanol and o-cresol over the entire composition range have been measured at 293, 303 and 313 K. Refractive index, density and ultrasonic velocity data have been used to evaluate the molar refraction deviation ΔR_{m}, deviation in ultrasonic velocity Δu, excess internal pressure π_{i}^{E}, excess molar enthalpy H_{m}^{E} and excess free volume V_{f}^{E}. The computed results of ΔR_{m}, Δu, π_{i}^{E}, H_{m}^{E} and V_{f}^{E} were fitted to the Redlich-Kister polynomial equation. These results suggest that specific strong interactions are taking place in THF + o-cresol mixture while dispersive forces seem to be responsible for behaviour of THF + methanol mixture. Further, experimental refractive index and density data of these mixtures were also used to test the validity of the empirical/semi-empirical relations and models for refractive index and density, respectively.

Refine search results

Structural Properties of Some Alkali Metal Hydrides at High Temperature and Pressure

High Pressure Phase Transition and Allied Behavior οf Samarium Compounds

TBI Calculations of the Elastic Properties and Structural Phase Transformation in Novel Materials: Yttrium Nitride

Modulation of radiation-induced biochemical changes in cerebrum of Swiss albino mice by Grewia asiatica

Modelling and Experimental Characterization of Processing Parameters in Vertical Twin Roll Casting of Aluminium Alloy A356

Volumetric, Optical, Acoustical and Viscometric Study of Molecular Association in Binary Mixtures of Butylamine with 1-Butanol and Tert-Butanol

Effect of van Hove Singularity on T_c in Rb doped C_{60}

Molecular Interaction Study of Binary Mixtures of THF with Methanol and o-Cresol - an Optical and Ultrasonic Study