scholarly journals Computational Modelling of Structural, Electronic, Optical and Vibrational Properties of PVK/C60 Nanoheterostructure Interfaces

2020 ◽  
Vol 11 (3) ◽  
pp. 10864-10884
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Computational Modelling ◽  
Phonon Modes ◽  
Functional Studies ◽  
Density Functional Perturbation Theory ◽  
Structural Differences ◽  
Dynamical Lattice ◽  
Quantum Espresso ◽  
Stacking Patterns

In this work, we present first-principles density functional studies of the dynamical properties of three nanoheterostructure interfaces of poly(9-vinylcarbazole)/fullerene (PVK/C60): PVK/C60(α), PVK/C60(β), and PVK/C60(γ). Linear response within density functional perturbation theory (DFPT), as implemented in the Quantum Espresso code, has been employed to explore the nature of permittivity, Born effective charges, polarizabilities, and vibrational frequency modes. The vibrational frequencies for the three nanoheterostructure interfaces were computed and their modes assigned. The phonon modes were also classified, and we showed that some important frequency modes are associated with C-C, CH2, and C−N stretching modes, among others. In addition, computed values of polarizability and permittivity for the nanoheterostructures were seen to have comparable values to that of literature for conjugated polymers. Conspicuous differing characteristics were noticed in the computed infrared and Raman absorption spectra for the three nanoheterostructures, which was due to the structural differences arising from their different stacking patterns. It is noted that the presence of the nitrogen atom plays a significant role in determining their dynamical lattice properties. The permittivity and polarizability tensors of PVK/C60(α), PVK/C60(β), and PVK/C60(γ) nanoheterostructures were found to be strongly anisotropic.

AB INITIO STUDY OF PHONON DISPERSION AND ELASTIC PROPERTIES OF L12 INTERMETALLICS Ti3Al AND Y3Al

2013 ◽  
Vol 27 (30) ◽  
pp. 1350224 ◽  
Author(s):  
N. ARIKAN ◽  
M. ERSEN ◽  
H. Y. OCAK ◽  
A. İYIGÖR ◽  
A. CANDAN ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Phonon Dispersion ◽  
High Symmetry ◽  
Generalized Gradient ◽  
Pressure Derivative ◽  
Phonon Dispersion Curves ◽  
Lattice Constants ◽  
Density Functional Perturbation Theory ◽  
Phonon Properties

In this paper, the structural, elastic and phonon properties of Ti 3 Al and Y 3 Al in L1 2( Cu 3 Al ) phase are studied by performing first-principles calculations within the generalized gradient approximation. The calculated lattice constants, static bulk moduli, first-order pressure derivative of bulk moduli and elastic constants for both compounds are reported. The phonon dispersion curves along several high-symmetry lines at the Brillouin zone, together with the corresponding phonon density of states, are determined using the first-principles linear-response approach of the density functional perturbation theory. Temperature variations of specific heat in the range of 0–500 K are obtained using the quasi-harmonic model.

scholarly journals New Zirconium Diboride Polymorphs—First-Principles Calculations

Materials ◽  
2020 ◽  
Vol 13 (13) ◽  
pp. 3022 ◽  
Author(s):  
Marcin Maździarz ◽  
Tomasz Mościcki
Keyword(s):  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Density Functional Theory Calculations ◽  
Zirconium Diboride ◽  
Point Of View ◽  
Phonon Modes ◽  
Functional Theory ◽  
Space Group

Two new hypothetical zirconium diboride (ZrB 2 ) polymorphs: (hP6-P6 3 /mmc-space group, no. 194) and (oP6-Pmmn-space group, no. 59), were thoroughly studied under the first-principles density functional theory calculations from the structural, mechanical and thermodynamic properties point of view. The proposed phases are thermodynamically stable (negative formation enthalpy). Studies of mechanical properties indicate that new polymorphs are less hard than the known phase (hP3-P6/mmm-space group, no. 191) and are not brittle. Analysis of phonon band structure and density of states (DOS) also show that the phonon modes have positive frequencies everywhere and the new ZrB 2 phases are not only mechanically but also dynamically stable. The estimated acoustic Debye temperature, Θ D , for the two new proposed ZrB 2 phases is about 760 K. The thermodynamic properties such as internal energy, free energy, entropy and constant-volume specific heat are also presented.

THEORETICAL INVESTIGATION OF THE ELASTIC PROPERTIES AND LATTICE DYNAMICS OF THE MgSxSe1-x ALLOY

2007 ◽  
Vol 21 (05) ◽  
pp. 249-259 ◽  
Author(s):  
K. BOUAMAMA ◽  
P. DJEMIA
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Local Density ◽  
Lattice Parameter ◽  
First Principles Calculations ◽  
Virtual Crystal Approximation ◽  
Functional Theory ◽  
Density Functional Perturbation Theory

Structural and elastic properties as well as lattice dynamics of ternary MgS x Se 1-x alloy have been studied using first-principles calculations. These are done using density functional theory (DFT) and density functional perturbation theory (DFPT) within the local density approximation (LDA) and employing the virtual-crystal approximation (VCA). We found that the lattice parameter, the elastic constants and the phonon frequencies follow a quadratic law in x.

Hydrogenation as a source of superconductivity in two-dimensional TiB2

2021 ◽  
pp. 2150057
Author(s):  
Hui Wang ◽  
Chen Pan ◽  
Sheng-Yan Wang ◽  
Hong Jiang ◽  
Yin-Chang Zhao ◽  
...  
Keyword(s):  
Perturbation Theory ◽  
Vibration Frequency ◽  
First Principles ◽  
Density Functional ◽  
Tensile Strain ◽  
2D Materials ◽  
Two Dimensional ◽  
First Principles Calculations ◽  
Density Functional Perturbation Theory ◽  
Potential Applications

Using first-principles calculations based on density functional perturbation theory, we demonstrate hydrogenation-induced superconductivity in monolayer TiB2H. Hydrogen adatoms destroy the Dirac state of monolayer TiB2 and monolayer TiB2H has a high vibration frequency. Monolayer TiB2H is a phonon-mediated superconductor. Monolayer TiB2H has a predicted [Formula: see text] of 8[Formula: see text]K, which further increases under external tensile strain. Thus, this study extends our understanding of superconductivity in two-dimensional (2D) materials and its potential applications.

scholarly journals First-principles study of solid methane at high pressure

BIBECHANA ◽  
2014 ◽  
Vol 12 ◽  
pp. 70-79 ◽  
Author(s):  
Nurapati Pantha ◽  
Jagaran Acharya ◽  
Narayan Prasad Adhikari
Keyword(s):  
High Pressure ◽  
Band Gap ◽  
First Principles ◽  
Density Functional ◽  
Wide Band ◽  
Orthorhombic Structure ◽  
Generalized Gradient ◽  
Reported Data ◽  
Quantum Espresso ◽  
Solid Methane

We study the structural and electronic properties of solid methane of space group P212121 at high pressure. The density-functional theory (DFT) based first-principles calculations within the Generalized Gradient Approximations (GGA) have been performed by using Quantum Espresso package. Our findings show that the solid methane in orthorhombic structure compresses fast at the first, and then slowly as a function of elevated hydrostatic pressure. The pressure-volume diagram agrees with the available previously reported data up to pressure of around 200 GPa. In orthorhombic structure, solid methane is a wide band gap insulator at low pressures (tens of GPa). The band gap decreases with increase in the pressure. At high pressure (around 900 GPa), the band gap decreases to semi-conductor range (1.78 eV). Our results reveal that methane to be metallic above the pressure coverage of the present study which is consistent to the interior of the giant planets. The band gap as a function of pressure (from the present work) agrees well with the previously reported data. DOI: http://dx.doi.org/10.3126/bibechana.v12i0.11779BIBECHANA 12 (2015) 70-79

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.

First-principle studies of the lattice dynamics of crystals, and related properties

2005 ◽  
Vol 220 (5/6) ◽  
Author(s):  
Xavier Gonze ◽  
Gian-Marco Rignanese ◽  
Razvan Caracas
Keyword(s):  
Perturbation Theory ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Computational Method ◽  
Dielectric Tensor ◽  
Atomic Temperature ◽  
Density Functional Perturbation Theory ◽  
Infra Red ◽  
Temperature Factors

AbstractThe crystal lattice is never rigid. Due to temperature, external fields or pressure, the nuclei vibrate, the lattice distorts, and instabilities can induce phase transitions. We review the basic concepts of density-functional perturbation theory, a computational method especially suited to determine from first-principles the microscopic parameters governing such behaviour. Then, we present the additional formalism leading to the following properties of minerals: the infra-red and Raman spectra; the prediction of (meta)stability or instability of a crystalline phase, based on the phonon spectrum; the computation of thermodynamics quantities like the free energy, entropy, specific heat; the atomic temperature factors. For each property, examples are given. When appropriate, we mention the computation of related properties, like dielectric tensor and Born effective charges that are needed to get infra-red spectra. Finally, we discuss briefly, on one hand, other applications of the density-functional perturbation theory, and, on the other hand, an alternative technique, the finite-difference computation of dynamical matrices.

Structural and Vibrational Properties of Manganese Sulfide

2013 ◽  
Vol 209 ◽  
pp. 186-189
Author(s):  
Brijmohan Y. Thakore ◽  
A.Y. Vahora ◽  
S.G. Khambholja ◽  
A.R. Jani
Keyword(s):  
Bulk Modulus ◽  
Density Functional ◽  
Local Density ◽  
Theoretical Calculations ◽  
Manganese Sulfide ◽  
High Symmetry ◽  
Isothermal Bulk Modulus ◽  
Pressure Derivative ◽  
Density Functional Perturbation Theory ◽  
Quantum Espresso

Structural properties of MnS have been studied using plane wave pseudopotential density functional theory as implemented in Quantum Espresso code. Local density approximation (LDA) along with ultrasoft pseudopotential has been used for total energy calculations. The calculated total energies are fitted to Murnaghan equation of state to calculate equilibrium lattice constant, isothermal bulk modulus and pressure derivative of isothermal bulk modulus for NaCl-type structure of MnS and compared with previous experimental and theoretical calculations and good agreement is achieved with those results. Phonon frequencies have also been derived for B1 phase of MnS along high symmetry directions using the density functional perturbation theory at ambient condition.

Phonon Dispersions of a Single-Wall (8,0) Carbon Nanotube: Effects of the Rotational Acoustic Sum Rule and of Surface Attachment

2004 ◽  
Vol 858 ◽  
Author(s):  
Nicolas Mounet ◽  
Nicola Marzari
Keyword(s):  
Carbon Nanotubes ◽  
First Principles ◽  
Lattice Dynamics ◽  
Density Functional ◽  
Single Walled Carbon Nanotubes ◽  
Vibrational Properties ◽  
Surface Attachment ◽  
Sum Rule ◽  
Density Functional Perturbation Theory ◽  
Walled Carbon Nanotubes

ABSTRACTThe lattice dynamics of single-walled carbon nanotubes (SWCNT) is studied from first-principles using density-functional perturbation theory (DFPT) at the GGA-PBE level. The phonon dispersions of a pristine, infinite zigzag (8,0) SWCNT are obtained and the effect of applying the rotational acoustic sum rule on vibrational properties is discussed. Finally we study the effects of covalent functionalizations on the SWCNT phonon frequencies by selectively increasing the effective mass of the carbon atoms that would link to the functional groups.

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