D.K Basa

Valence electronic structure of Ti, Cr, Fe and Co in some alloys from Kβ-to-Kα X-ray intensity ratio studies

Abstract Kβ-to-Kα X-ray intensity ratios of Ti, Cr, Fe and Co in pure metals and in Cr0.26Fe0.74, Cr0.80Co0.20 and Ti0.80Cr0.20 alloys have been measured following excitation by 59.54 keV γ-rays from a 7400 MBq (200 mCi) 241 Am point-source. The valence electronic structure of Ti, Cr, Fe and Co in the samples have been evaluated by the comparison of the measured Kβ-to-Kα intensity ratios with the results of multiconfiguration Dirac–Fock calculations performed for various electronic configurations of these metals. The 3d-electron populations obtained for pure metallic Ti, Cr, Fe and Co agree well with the results of band structure calculations of Papaconstantopoulos (Handbook of band structure of elemental solids, Plenum Press, New York, 1986). Our analysis indicates significant increase of 3d-electron population of Ti, Cr and Fe in the alloys with respect to the pure metals, except for Cr in Cr0.26Fe0.74 where the absolute 3d-electron population of Cr is found to be slightly less as compared to that of pure Cr. It has been found that to reliably explain the observed changes in the valence electronic structure of Ti, Cr, Fe and Co in their alloys it is necessary to take into account the rearrangement of electrons between 3d and (4s,4p) states of individual metal atoms, while the transfer of 3d electrons from one element to the other element can be neglected.

Kβ-to-Kα X-ray intensity ratio studies on the changes of valence electronic structures of Ti, V, Cr, and Co in their disilicide compounds

Abstract Kβ-to-Kα X-ray intensity ratios of Ti, V, Cr, and Co in pure metals and their disilicide compounds have been measured following excitation by 59.54 keV γ-rays from a 200 mCi 241Am point-source. The Kβ-to-Kα intensity ratios of all these metals in the disilicide compounds are found to be less than the corresponding ratios for pure metals. Comparison of the measured Kβ-to-Kα intensity ratios for the disilicides and pure metals with the multiconfiguration Dirac–Fock calculations indicates increase of the 3d electron populations of Ti, V, Cr, and Co in the disilicides from their pure metal values suggesting the rearrangement of electrons between 3d and 4s states of the individual metal atom. This rearrangement is found to be opposite to that observed in our previously reported work on NiSi2 and CuSi2.

Valence electronic structure of Fe and Ni in FexNi1−x alloys from relative K X-ray intensity studies

Abstract Kβ-to-Kα X-ray intensity ratios of Fe and Ni in pure metals and in FexNi1−x alloys for different compositions x (x=0.20, 0.50, 0.58) have been measured following excitation by 59.54xa0keV γ-rays from a 200xa0mCi 241Am point-source. For certain alloy compositions the Kβ-to-Kα intensity ratios of Fe and Ni differ considerably from those obtained for the pure metals. The 3d electron populations of Fe and Ni have been estimated by comparing the measured Kβ-to-Kα ratios with the results of multi-configuration Dirac–Fock (MCDF) calculations. Our results for the 3d electron populations of solid iron and nickel agree reasonably well with the earlier results of band structure calculations. In the case of alloys significant changes in the 3d electron population of Fe and Ni are observed for certain alloy compositions. These changes can be explained by assuming rearrangement of electrons between 3d and (4s,4p) valence band states of the individual metal atoms. For the alloy composition x=0.2 the change in the 3d electron population of Ni is the largest and has the opposite direction than in the case of other two alloy compositions. The totally different valence electronic structure of Fe0.2Ni0.8 alloy seems to explain the special magnetic properties of this alloy.

Charge transfer studies in V3Si, Cr3Si and FeSi

Abstract Kβ -to- Kα X-ray intensity ratios of V , Cr and Fe in pure metals and in V 3 Si , Cr 3 Si and FeSi have been measured for understanding the charge transfer / delocalization phenomena in the silicide compounds. Comparison of the measured ratios for V with Multi Configuration Dirac–Fock calculations indicates a small amount of charge transfer (0.54±0.25 electrons per V atom) from vanadium to silicon in V 3 Si which is in qualitative agreement with the results of LCAO band structure calculation of Bisi and Chiao (O. Bisi and L.W. Chiao, Phys. Rev. B, 25 (1982) 4943). However, previous experimental studies on charge density, Compton profile and theoretical calculations based on linear APW method suggested charge transfer from Si to V with differing amounts which disagree with our present result. Alternatively the result for V 3 Si can also be explained as due to rearrangement of electrons between 3 d and 4 s states of vanadium. Our result for Cr 3 Si suggests an increase of 3 d electrons of Cr by about 1.02±0.32 either due to transfer of electrons from Si to Cr or transfer of electrons from 4 s state to 3 d state of Cr . Our experimental result for FeSi suggests no change in the valence electronic structure of Fe .

Valence electronic structure of Mn in undoped and doped lanthanum manganites from relative K x-ray intensity studies

Abstract Relative K X-ray intensities of Mn in Mn, MnO2, LaMnO3 and La0.7B0.3MnO3 (B = Ca, Sr and Ce) systems have been measured following excitation by 59.54 keV γ-rays from a 200 mCi 241Am point-source. The measured results for the compounds deviate significantly from the results of pure Mn. Comparison of the experimental data with the multi-configuration Dirac–Fock (MCDF) effective atomic model calculations indicates reasonable agreement with the predictions of ionic model for the doped manganites except that the electron-doped La0.7Ce0.3MnO3 and hole-doped La0.7Ca0.3MnO3 compounds show some small deviations. The results of MnO2 and LaMnO3 deviate considerably from the predictions of the ionic model. Our measured Kβ/Kα ratio of Mn in La0.7Ca0.3MnO3 cannot be explained as a linear superposition of Kβ/Kα ratios of Mn for the end members which is in contrast to the recent proposal by Tyson et al. from their Mn Kβ spectra.Relative

Quantum well model and variation of the optical band gap in hydrogenated amorphous silicon carbon alloy films

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Relative K x-ray intensity studies of the valence electronic structure of 3 d transition metals

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K β − t o − K α x-ray intensity ratio studies of the valence electronic structure of Fe and Ni in Fe x Ni 1 − x alloys

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Studies on the composition of ancient Indian punch-marked silver coins

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EDXRF study of Indian punch-marked silver coins

Mn