scholarly journals Impurity Centers in Oxides Investigated by γ-γ Perturbed Angular Correlation Spectroscopy and Ab Initio Calculations

2011 ◽  
Vol 311 ◽  
pp. 62-104 ◽  
Author(s):  
Alberto F. Pasquevich ◽  
Mario Rentería
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Angular Correlation ◽  
Density Functional ◽  
Perturbed Angular Correlation ◽  
Correlation Spectroscopy ◽  
Nano Particles ◽  
Defect Complexes ◽  
Probe Site ◽  
Impurity Sites

In this chapter Perturbed Angular Correlation (PAC) experiments on binary oxides are described. These experiments provide local-scale fingerprints about the formation, identification, and lattice environment of defect complexes at the PAC probe site. The potential of the PAC observations in conjunction with ab initio calculations is shown. Measurements of the electric-field gradient at impurity sites using111Cd and181Ta probes are reviewed. Special attention is paid to oxides with the bixbyite structure. The case of In2O3is particularly analyzed. Results obtained with HfO2, in form of coarse grain or nano particles, are described. The potential results that can be obtained from Density Functional Theory ab initio calculations in doped systems are shown describing the main results observed in many impurity-host systems.

Acceptor‐defect complexes in GaAs studied by perturbed angular correlation spectroscopy

1989 ◽  
Vol 55 (22) ◽  
pp. 2301-2303 ◽  
Author(s):  
A. Baurichter ◽  
M. Deicher ◽  
S. Deubler ◽  
D. Forkel ◽  
H. Plank ◽  
...  
Keyword(s):  
Angular Correlation ◽  
Perturbed Angular Correlation ◽  
Correlation Spectroscopy ◽  
Perturbed Angular Correlation Spectroscopy ◽  
Defect Complexes ◽  
Acceptor Defect

scholarly journals Phonons in Short-Period GaN/AlN Superlattices: Group-Theoretical Analysis, Ab initio Calculations, and Raman Spectra

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 286
Author(s):  
Valery Davydov ◽  
Evgenii Roginskii ◽  
Yuri Kitaev ◽  
Alexander Smirnov ◽  
Ilya Eliseyev ◽  
...  
Keyword(s):  
Theoretical Analysis ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Raman Spectra ◽  
Density Functional ◽  
Structural Characteristics ◽  
Vibrational Modes ◽  
Phonon Modes ◽  
Short Period ◽  
Group Theoretical Analysis

We report the results of experimental and theoretical studies of phonon modes in GaN/AlN superlattices (SLs) with a period of several atomic layers, grown by submonolayer digital plasma-assisted molecular-beam epitaxy, which have a great potential for use in quantum and stress engineering. Using detailed group-theoretical analysis, the genesis of the SL vibrational modes from the modes of bulk AlN and GaN crystals is established. Ab initio calculations in the framework of the density functional theory, aimed at studying the phonon states, are performed for SLs with both equal and unequal layer thicknesses. The frequencies of the vibrational modes are calculated, and atomic displacement patterns are obtained. Raman spectra are calculated and compared with the experimental ones. The results of the ab initio calculations are in good agreement with the experimental Raman spectra and the results of the group-theoretical analysis. As a result of comprehensive studies, the correlations between the parameters of acoustic and optical phonons and the structure of SLs are obtained. This opens up new possibilities for the analysis of the structural characteristics of short-period GaN/AlN SLs using Raman spectroscopy. The results obtained can be used to optimize the growth technologies aimed to form structurally perfect short-period GaN/AlN SLs.

Defects in CdS: In detected by perturbed angular correlation spectroscopy (PAC)

1991 ◽  
Vol 50 (1-4) ◽  
pp. 159-164 ◽  
Author(s):  
R. Magerle ◽  
M. Deicher ◽  
U. Desnica ◽  
R. Keller ◽  
W. Pfeiffer ◽  
...  
Keyword(s):  
Angular Correlation ◽  
Perturbed Angular Correlation ◽  
Correlation Spectroscopy ◽  
Perturbed Angular Correlation Spectroscopy

scholarly journals Magnetic Properties and the Electronic Structure of the Gd0.4Tb0.6Co2 Compound

Materials ◽  
2020 ◽  
Vol 13 (23) ◽  
pp. 5481
Author(s):  
Marcin Sikora ◽  
Anna Bajorek ◽  
Artur Chrobak ◽  
Józef Deniszczyk ◽  
Grzegorz Ziółkowski ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Photoelectron Spectroscopy ◽  
Density Functional ◽  
Magnetic Measurements ◽  
Plane Waves ◽  
Full Potential ◽  
Theory Approach ◽  
Xps Spectra

We report on the comprehensive experimental and theoretical studies of magnetic and electronic structural properties of the Gd0.4Tb0.6Co2 compound crystallization in the cubic Laves phase (C15). We present new results and compare them to those reported earlier. The magnetic study was completed with electronic structure investigations. Based on magnetic isotherms, magnetic entropy change (ΔSM) was determined for many values of the magnetic field change (Δμ0H), which varied from 0.1 to 7 T. In each case, the ΔSM had a maximum around room temperature. The analysis of Arrott plots supplemented by a study of temperature dependency of Landau coefficients revealed that the compound undergoes a magnetic phase transition of the second type. From the M(T) dependency, the exchange integrals between rare-earth R-R (JRR), R-Co (JRCo), and Co-Co (JCoCo) atoms were evaluated within the mean-field theory approach. The electronic structure was determined using the X-ray photoelectron spectroscopy (XPS) method as well as by calculations using the density functional theory (DFT) based Full Potential Linearized Augmented Plane Waves (FP-LAPW) method. The comparison of results of ab initio calculations with the experimental data indicates that near TC the XPS spectrum collects excitations of electrons from Co3d states with different values of exchange splitting. The values of the magnetic moment on Co atoms determined from magnetic measurements, estimated from the XPS spectra, and results from ab initio calculations are quantitatively consistent.

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