M.C. Mishra

A study of electron momentum density distribution in Al2O3 ceramic

A study of electron momentum density distribution in α-Al2O3 ceramic using Compton spectroscopy is presented in this work. Measurements have been carried out using 59.54 keV gamma-rays emanating from an Am241 source. Calculations have been performed on the basis of the ab-initio linear combination of atomic orbitals (LCAO) method embodied in the CRYSTAL code. The correlation scheme proposed by Perdew–Burke–Ernzerhof was adopted. The exchange was treated following the Becke scheme. The Hartree–Fock and hybrid schemes were also applied to the compound. All the schemes yielded results that are in good agreement with the measurements. The agreement with experiment is, however, better with the hybrid B3LYP (Lee–Yang–Parr) scheme. Ionic model calculations for a number of configurations of (Al+x)2(O−2x/3)3 (2.75≤x≤3 in steps of 0.125) were also performed utilizing free atom profiles. The ionic model suggests transfer of 2.875 electrons from the valence sp state of Al to the p state of O.

Electron momentum density distribution in Cd3P2

Abstract A study of electron momentum density distribution in Cd 3 P 2 is reported in this work. The measurement of Compton profile is carried out on a polycrystalline sample using 59.54 keV gamma-rays emanating from an 241 Am radioisotope. The theoretical calculations are performed using linear combination of atomic orbitals method following the Hartree–Fock and a posteriori density functional theories. The spherically averaged theoretical Compton profiles are in good agreement with the measurement. The best agreement is, however, shown by the Hartree–Fock scheme. Simple ionic model calculations for a number of configurations ( Cd + x ) 3 ( P − 3 x / 2 ) 2 ( 0.0 ⩽ x ⩽ 2.0 in step of 0.2) are also performed utilizing free atom profiles. The ionic model supports transfer of 2.0 electrons per Cd atom from 5 s state to 3 p state of P.

Electronic structure of nano-sized ZnO: A Compton profile study

The electronic structure of nano-sized ZnO using Compton scattering technique is reported. The nano-crystalline ZnO of size 10.5 nm is synthesized using the chemical route and characterized by XRD, SEM, TEM probes. Using 59.54 keV gamma-rays, the Compton profile measurements are performed on nano-sized as well as bulk ZnO. The present study reveals the narrower electron momentum density in nano-sized ZnO as compared to bulk sample. The ionic model based free atom Compton profiles for a number of configurations of Zn+xO−x (0.0 ≤ x ≤ 2.0) are also performed to estimate the charge transfer on compound formation. The present study suggests different amount of charge transfer from Zn to O atom in the nano-sized and bulk ZnO.

Electronic Properties of ZnO: Band Structure and Directional Compton Profiles

The electronic band structure and directional Compton profiles (DCPs) of ZnO are studied in this work. Calculations are performed considering a set of three schemes based on density functional theory (DFT), the Hartree–Fock (HF) method, and a hybrid scheme. All band structures predict direct bandgaps. The best agreement with experiment is, however, shown by the hybrid scheme. The three schemes are also applied to compute DCPs along [100], [110], and [001] directions. These are compared with measurements made on single crystals of ZnO employing a 59.54 keV gamma-ray Compton spectrometer. Calculations overestimate the momentum density in the low-momentum region while underestimate the anisotropies. Positions of extremes in anisotropies deduced from calculations are well reproduced by the measured anisotropies in some cases. Within the experimental limits, the DCPs from the HF method are in better agreement with the measurements compared with DFT.

Compton Profile Study of Intermetallic Ti3Al

The Compton scattering measurement on intermetallic alloy Ti3Al is reported in this work. The measurement is made using 59.54 keV gamma‐rays from Am241 source. Theoretical calculation of Compton profile is also performed employing CRYSTAL code within the framework of density functional theory to compare with the measurement. The theoretical profile of the alloy is also synthesized following the superposition model taking the published Compton profiles of elemental solids from the APW method. The experimental study of charge transfer in the alloys has also been done by performing the experimental Compton profile measurements on Ti and Al following the superposition model and charge transfer from Al to Ti is clearly seen on the alloy formation.

Compton profile study of polycrystalline ZnBr2

The first ever Compton profile study of polycrystalline ZnBr2 is presented in this paper. The measurement of polycrystalline sample of ZnBr2 is performed using 59.54 keV gamma‐rays emanating from an 241Am radioisotope. Theoretical calculations are performed following the Ionic model calculations for a number of configurations Zn+xBr2−x/2 (0.0≤x≤2.0 in step of 0.5) utilizing free atom profiles. The ionic model suggest transfer of 2.0 electrons from 4 s state of Zn to 4 p state of two Br atoms. The autocorrelation function B(z) is also derived from experiment and the most favoured ionic valence Compton profiles.