Raman active phonon modes and heat capacities of Ti2AlC and Cr2AlC ceramics: first-principles and experimental investigations

2005 ◽  
Vol 86 (10) ◽  
pp. 101902 ◽  
Author(s):  
Jingyang Wang ◽  
Yanchun Zhou ◽  
Zhijun Lin ◽  
Fanling Meng ◽  
Feng Li
Keyword(s):  
First Principles ◽  
Heat Capacities ◽  
Experimental Investigations ◽  
Phonon Modes ◽  
Raman Active Phonon

First-principles study on the dielectric and transport properties of the LiNbO3-type CdPbO3

2017 ◽  
Vol 31 (05) ◽  
pp. 1750032
Author(s):  
Jing Zhang ◽  
San Huang Ke ◽  
Derwyn A. Rowlands
Keyword(s):  
Transport Properties ◽  
First Principles ◽  
Electronic Devices ◽  
Differential Resistance ◽  
Uniaxial Crystal ◽  
Dielectric Constants ◽  
First Principles Calculation ◽  
Electric Transport ◽  
Phonon Modes ◽  
Ir And Raman

Using first-principles calculation method, we have investigated the zone-center phonon modes, dielectric and transport properties of the LiNbO3-type CdPbO3. The results show that the relatively large peaks of infrared (IR) and Raman spectra mainly come from the [Formula: see text] and [Formula: see text] modes, respectively. The dielectric constant calculations reveal that this compound is positive uniaxial crystal and has the large dielectric constants. By investigating the electric transport properties using gold as electrode, the interesting negative differential resistance (NDR) effect can be observed, which reveals this compound should have important application in semiconducting electronic devices.

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.

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.

scholarly journals Structural Stability of Functionalized Silicene Nanoribbons with Normal, Reconstructed, and Hybrid Edges

2016 ◽  
Vol 2016 ◽  
pp. 1-8 ◽  
Author(s):  
Sadegh Mehdi Aghaei ◽  
Ingrid Torres ◽  
Irene Calizo
Keyword(s):  
Structural Stability ◽  
First Principles ◽  
Experimental Investigations ◽  
First Principles Calculations ◽  
Zigzag Edge ◽  
Edge Structure ◽  
Practical Applications ◽  
Potential Applications ◽  
Silicene Nanoribbons ◽  
Significant Attention

Silicene, a novel graphene-like material, has attracted a significant attention because of its potential applications for nanoelectronics. In this paper, we have theoretically investigated the structural stability of edge-hydrogenated and edge-fluorinated silicene nanoribbons (SiNRs) via first-principles calculations. Various edge forms of SiNRs including armchair edge, zigzag edge, Klein edge, reconstructed Klein edge, reconstructed pentagon-heptagon edge, and hybrid edges have been considered. It has been found that fully fluorinated Klein edge SiNRs, in which each edge Si atom is terminated by three fluorine atoms, are the most stable structure. We also discovered that a hybrid edge structure of trihydrogenated Klein edge and dihydrogenated zigzag edge can increase the nanoribbon’s stability up to that of dihydrogenated armchair edge SiNR, which is known as the most stable edge-hydrogenated structure. With the attractive properties of silicene for practical applications, the obtained results will advance experimental investigations toward the development of silicene based devices.

scholarly journals Relaxation dynamics of deeply supercooled confined water in l,l-diphenylalanine micro/nanotubes

2015 ◽  
Vol 17 (48) ◽  
pp. 32126-32131 ◽  
Author(s):  
P. M. G. L. Ferreira ◽  
M. S. Ishikawa ◽  
S. Kogikoski ◽  
W. A. Alves ◽  
H. Martinho
Keyword(s):  
Temperature Dependence ◽  
Low Frequency ◽  
Confined Water ◽  
Relaxation Dynamics ◽  
Phonon Modes ◽  
Raman Active Phonon

The temperature dependence (10–290 K) of the low-frequency (20–150 cm−1) Raman-active phonon modes of deeply supercooled confined water in l,l-diphenylalanine micro/nanotubes was analyzed.

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