Assignment of Raman-active vibrational modes of tetragonal mackinawite: Raman investigations and ab initio calculations

RSC Advances ◽  
2014 ◽  
Vol 4 (49) ◽  
pp. 25827-25834 ◽  
Author(s):  
Y. El Mendili ◽  
B. Minisini ◽  
A. Abdelouas ◽  
J.-F. Bardeau
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Density Functional ◽  
Direct Methods ◽  
Vibrational Modes ◽  
Dispersion Correction ◽  
Density Functional Perturbation Theory ◽  
Calculation Results

We report on the first assignment of the Raman-active vibrational modes of mackinawite using Density Functional Perturbation Theory and direct methods with BLYP + dispersion correction. Based on experimental data and calculation results, the Raman bands were assigned as 236 cm−1 (B1g), 256 cm−1 (Eg), 376 cm−1 (A1g) and 395 cm−1 (Eg).

scholarly journals Thermodynamic properties of pure and doped (B, N) graphene

RSC Advances ◽  
2016 ◽  
Vol 6 (15) ◽  
pp. 12158-12168 ◽  
Author(s):  
Sarita Mann ◽  
Pooja Rani ◽  
Ranjan Kumar ◽  
Girija S. Dubey ◽  
V. K. Jindal
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Thermodynamic Properties ◽  
Ab Initio ◽  
Graphene Sheet ◽  
Density Functional ◽  
Thermodynamical Properties ◽  
Density Functional Perturbation Theory ◽  
Doped Graphene

Ab initio density functional perturbation theory (DFPT) has been employed to study the thermodynamical properties of pure and doped graphene sheet and the results have been compared with available theoretical and experimental data.

Thermoelectric and piezoelectric properties of the predicted AlxIn1−xN composites based on ab initio calculations

2017 ◽  
Vol 19 (36) ◽  
pp. 24613-24625 ◽  
Author(s):  
Yee Hui Robin Chang ◽  
Tiem Leong Yoon ◽  
Thong Leng Lim ◽  
Moi Hua Tuh ◽  
Eong Sheng Goh
Keyword(s):  
Perturbation Theory ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Piezoelectric Properties ◽  
Boltzmann Transport ◽  
Density Functional Perturbation Theory ◽  
Theoretical Investigations ◽  
Piezoelectric Characteristics

Theoretical investigations of the thermoelectric and piezoelectric characteristics in the AlxIn1−xN system have been carried out based on a first principles approach in combination with the semi-classical Boltzmann transport concept and density functional perturbation theory.

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.

First-Principles Study of Structural and Vibrational Properties of α-SiO2 under Pressure

2015 ◽  
Vol 775 ◽  
pp. 191-196
Author(s):  
Xiao Wei Lei ◽  
Yong Song ◽  
Kuo Yang ◽  
Hui Zhao
Keyword(s):  
High Pressure ◽  
Perturbation Theory ◽  
Infrared Spectra ◽  
First Principles ◽  
Linear Response ◽  
Density Functional ◽  
Vibrational Properties ◽  
Vibrational Modes ◽  
Density Functional Perturbation Theory ◽  
Good Agreement

Using first principles approach, we present the structural, vibrational and dielectric properties of α-SiO2. The calculations have been carried out within the density functional perturbation theory and linear response formalism using the norm-concerving pseudopotentials and a plane wave basis. All the vibrational modes identified are in good agreement with experiment. The calculated infrared spectra are also in good agreement with available experimental results both for the positions and the intensities of the main peaks. We find that the modes Eu7 and A2u4 splits in two respectively at high hydrostaticpressures. Then we calculate the infrared spectra under high pressure of different orientations. The vibrational modes in different phase transitions are reported and discussed respectively.

Thermodynamics of Stable and Metastable Cu-O-H Compounds

2011 ◽  
Vol 172-174 ◽  
pp. 973-978 ◽  
Author(s):  
Pavel A. Korzhavyi ◽  
Inna Soroka ◽  
Mats Boman ◽  
Börje Johansson
Keyword(s):  
Experimental Data ◽  
Perturbation Theory ◽  
Physical Properties ◽  
Density Functional ◽  
Metastable Phase ◽  
Experimental Studies ◽  
Ambient Conditions ◽  
Phonon Spectra ◽  
Density Functional Perturbation Theory ◽  
Good Agreement

We apply density functional perturbation theory together with experimental studies in order to investigate the structure and physical properties of possible stable and metastable copper(I) compounds with oxygen and hydrogen. Copper(I) hydride, CuH, is found to be a metastable phase which decomposes at ambient conditions and exhibiting a semiconducting gap in the electronic spectrum. The calculated structure and phonon spectra are found to be in good agreement with experimental data. The phonon spectra of a novel metastable phase, copper(I) hydroxide, are also determined.

Phonon Thermal Transport in Bulk and Nanostructured Materials From First Principles

2008 ◽  
Author(s):  
D. A. Broido ◽  
Natalio Mingo ◽  
Derek Stewart
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Nanostructured Materials ◽  
Thermal Transport ◽  
Density Functional ◽  
Thermal Conductance ◽  
Density Functional Perturbation Theory ◽  
Molecular Dynamics Calculations ◽  
Substitutional Defects ◽  
Silicon And Germanium

Current theories of phonon thermal transport in nanomaterials are often based on highly parametrized approximations or on purely classical molecular dynamics calculations. We present a rigorous theoretical approach to accurately describe phonon thermal transport in bulk and nanostructured materials. This technique is based on Boltzmann and non-equilibrium Green’s function calculations of thermal transport, and employs ab-initio calculations of harmonic and anharmonic interatomic force constants using density functional perturbation theory. The approach has been applied to bulk semiconductors, where excellent agreement is obtained between the calculated and measured intrinsic lattice thermal conductivities of silicon and germanium without any adjustable parameters. In addition, ab initio calculations of phonon thermal conductance in carbon nanotubes with isolated Stone-Wales and substitutional defects are presented and discussed.

Ab-initio Calculations to Model Anomalous Fluorine Behavior

2002 ◽  
Vol 717 ◽  
Author(s):  
Milan Diebel ◽  
Scott T. Dunham
Keyword(s):  
Experimental Data ◽  
Density Functional Theory ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Ground State ◽  
Fluorine Atom ◽  
Density Functional ◽  
Defect Structures ◽  
Functional Theory ◽  
Shallow Junctions

AbstractImplanted fluorine has been observed to behave unusually in silicon, manifesting apparent uphill diflusion [1]. We are further motivated to understand the behavior of implanted fluorine in silicon by experiments which suggest that fluorine reduces boron diflusion [2, 3, 4, 5] and enhances boron activation in shallow junctions [2, 3]. In order to investigate fluorine behavior, we calculated the energy of fluorine defect structures in the framework of density functional theory (DFT). Besides identifying the ground-state con.guration of a single fluorine atom in silicon, a set of energetically favorable fluorine defect structures were found. The latter strongly suggests a distinct fluorine diflusion mechanism, which was implemented in a continuum diflusion simulation and compared to experimental data.

Calculations and Experimental Studies of TAGzT under High Pressure

MRS Advances ◽  
2016 ◽  
Vol 1 (17) ◽  
pp. 1227-1232
Author(s):  
I.G. Batyrev ◽  
R.C. Sausa
Keyword(s):  
High Pressure ◽  
Perturbation Theory ◽  
Density Functional ◽  
Ambient Pressure ◽  
Experimental Studies ◽  
Vibrational Modes ◽  
Density Functional Perturbation Theory ◽  
Potential Formalism ◽  
Pseudo Potential ◽  
Raman And Ir Spectroscopy

ABSTRACTWe studied TAGzT theoretically using density functional perturbation theory within the plane-wave-pseudo-potential formalism and experimentally by Raman and IR spectroscopy at ambient and high pressure. The modeled spectra predict reasonably well the experimental spectra at ambient pressure and the Raman vibrational modes at pressures up to 25 GPa. We report the effects of pressure on volume, Raman and IR vibrational modes, and charge distribution of TAGzT.

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