ChemInform Abstract: Specific Heat of Amorphous Silica within the Harmonic Approximation.

ChemInform ◽  
2010 ◽  
Vol 30 (30) ◽  
pp. no-no
Author(s):  
Juergen Horbach ◽  
Walter Kob ◽  
Kurt Binder
Keyword(s):  
Specific Heat ◽  
Amorphous Silica ◽  
Harmonic Approximation

scholarly journals Specific Heat of Amorphous Silica within the Harmonic Approximation

1999 ◽  
Vol 103 (20) ◽  
pp. 4104-4108 ◽  
Author(s):  
Jürgen Horbach ◽  
Walter Kob ◽  
Kurt Binder
Keyword(s):  
Specific Heat ◽  
Amorphous Silica ◽  
Harmonic Approximation

A study of Raman spectroscopy and low-temperature specific heat in gel-synthesized amorphous silica

2001 ◽  
Vol 280 (1-3) ◽  
pp. 249-254 ◽  
Author(s):  
A. Bartolotta ◽  
G. Carini ◽  
G. D'Angelo ◽  
M. Ferrari ◽  
A. Fontana ◽  
...  
Keyword(s):  
Raman Spectroscopy ◽  
Low Temperature ◽  
Specific Heat ◽  
Amorphous Silica ◽  
Low Temperature Specific Heat

Ab Initio Study of the Phonon Frequency, Electrical and Thermal Properties of TiN

2012 ◽  
Vol 155-156 ◽  
pp. 291-297
Author(s):  
Xin Tan ◽  
Yu Qing Li ◽  
Xue Jie Liu
Keyword(s):  
Electronic Structure ◽  
Thermal Properties ◽  
Specific Heat ◽  
Density Functional ◽  
Correlation Energy ◽  
Phonon Dispersion ◽  
Harmonic Approximation ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Phonon Spectra

With a motivation to understand microscopic aspects of TiN relevant to the electronic structure, phonon and thermal properties of transition metal nitride TiN superlattices, we determine its electronic structure, phonon spectra and thermal properties using first-principles calculations based on density functional theory with a generalized gradient approximation of the exchange correlation energy. We find that the electronic bands crossed by EF are half occupied, TiN has the ability of taking part in chemical reactions and also has the surface activity; A large gap in its phonon spectra, anomalies in the phonon dispersion of metallic TiN, manifested as dips in acoustic branches, but it do not contain soft modes in any direction; The specific heat (Cv) of TiN rises rapidly at low temperatures, the Cv values of the material, is identical to the Dulong-Petit value at high temperatures. Under the quasi-harmonic approximation (QHA), the thermal expansion, specific heat and bulk modulus B(T) are obtained, and the B(T) decreases along with the increase of temperature.

THE AB INITIO CALCULATION OF THE DYNAMICAL AND THE THERMODYNAMIC PROPERTIES OF THE ZINC-BLENDE GaX (X=N, P, As AND Sb)

2012 ◽  
Vol 01 (03) ◽  
pp. 1250026
Author(s):  
Y. BOUHADDA ◽  
A. BENTABET ◽  
N. E. FENINECHE ◽  
Y. BOUDOUMA
Keyword(s):  
Thermodynamic Properties ◽  
Specific Heat ◽  
Ab Initio ◽  
Lattice Dynamics ◽  
Phonon Frequency ◽  
Harmonic Approximation ◽  
Simulation Method ◽  
Constant Volume ◽  
Zinc Blende ◽  
Good Agreement

By this work, we aim to study the dynamical and the thermodynamic properties of the zinc-blende GaX ( X = N , P , As and Sb ) using the Ab initio simulation method. Indeed, we studied the lattice dynamics, the constant-volume specific heat (Cv), the internal energy (U), the entropy (S) and the free energy (F). The observed differences between the properties of GaX elements were discussed. Our results and the available literature data (theoretical and experimental) seems to be in good agreement. Moreover, Cv, U, F and S were calculated by using the harmonic approximation in the calculation of the dynamic lattice vibration. The good agreement between our results of both the phonon frequency, the constant-volume specific heat and the experimental data allows us to conclude that our results of S, U and F of GaX were well predicted.

Ab initio investigation of the electronic, lattice dynamic and thermodynamic properties of ScCd intermetallic alloy

2016 ◽  
Vol 30 (24) ◽  
pp. 1650175
Author(s):  
B. I. Adetunji ◽  
A. S. Olayinka ◽  
J. B. Fashae ◽  
V. C. Ozebo
Keyword(s):  
Heat Capacity ◽  
Thermodynamic Properties ◽  
Specific Heat ◽  
Density Of States ◽  
Specific Heat Capacity ◽  
Density Functional ◽  
Phonon Dispersion ◽  
Harmonic Approximation ◽  
Generalized Gradient ◽  
Vibrational Free Energy

The electronic structures, lattice dynamics and thermodynamic properties of rare-earth intermetallic ScCd alloy are studied by the first-principles plane-wave pseudopotential method within the generalized gradient approximation in the framework of density functional pertubation theory. The band structure, density of states, phonon dispersion frequencies, vibrational free energy [Formula: see text], specific heat capacity [Formula: see text] and entropy are studied between 0 K and 1500 K. Finally, using the calculated phonon density of states, the thermodynamic properties are determined within the quasi-harmonic approximation and a value of 47.9 (J/mol⋅K) at 300 K for specific heat capacity of ScCd is predicted.

Physical Properties of Confined Silicon Structures Using EDIP

2006 ◽  
Author(s):  
Jose´ Pascual-Gutie´rrez ◽  
Jayathi Y. Murthy ◽  
Raymond Viskanta
Keyword(s):  
Thin Films ◽  
Physical Properties ◽  
Specific Heat ◽  
Silicon Nanowires ◽  
Interatomic Potential ◽  
Harmonic Approximation ◽  
Two Dimensions ◽  
Dynamical Matrix ◽  
Free Standing ◽  
Three Body

Physically confined structures such as thin films and nanowires are becoming increasingly important in the energy and electronics sectors. This has resulted from the ability to tailor nanostructures to yield physical properties that are significantly different from bulk. The main focus of this work is to examine how physical confinement in one and two dimensions affects the phonon wave vector spectrum within the first Brillouin zone of silicon thin films and silicon nanowires. Dispersion curves as well as density of states (DOS) are obtained using the dynamical matrix approach and a harmonic approximation to the three-body environmentally-dependent interatomic potential (EDIP). It is also shown how these changes in the phonon spectrum for both films and wires affect the volumetric specific heat with respect to bulk. The simulations are carried out assuming ideal free-standing boundary conditions. It is shown that confinement effects on the phonon specific heat are only important below 5 mm for both silicon films and wires.

ANALYSIS OF HEAT CAPACITY OF YBa2Cu3O7-δ SUPERCONDUCTORS: ROLE OF LATTICE AND ELECTRON CONTRIBUTION

2006 ◽  
Vol 20 (20) ◽  
pp. 2909-2920 ◽  
Author(s):  
DINESH VARSHNEY
Keyword(s):  
Heat Capacity ◽  
Specific Heat ◽  
Cuprate Superconductors ◽  
Fluid Model ◽  
Harmonic Approximation ◽  
Mean Field ◽  
Lattice Contribution ◽  
Electronic Term ◽  
Two Fluid Model ◽  
Two Fluid

Observed temperature-dependent heat capacity C (T) behavior of high-Tc YBa 2 Cu 3 O 7-δ cuprate superconductors has been theoretically analyzed in the temperature domain 70 ≤ T ≤ 110 K . Calculations of C (T) have been made within the two component scheme: one is the Fermionic term and the other the Bosonic (phonon) contribution. While estimating the electronic term, we use a mean field step and follow two-fluid model below and above Tc. Later on, the lattice heat capacity is estimated within harmonic approximation for high temperature expansion (T > θ/2π), the model has only one free parameter, the moments of phonon density of states. Within the two-fluid model for electronic specific heat along with reported γ value leads to a sharp discontinuity at Tc. The Coulomb correlations and electron-phonon coupling strength have significant implications on the γ. Henceforth, the present numerical analysis of specific heat from the present model shows similar results as those revealed from experiments. The accurate fitting of the specific heat data reveals that it is possible to decompose the documented specific heat into dominant lattice contribution and electronic channel. However, the specific heat from electronic term is only a fraction of lattice specific heat in YBa 2 Cu 3 O 7-δ high-Tc superconductors.

Amorphous silica coating on α-alumina particles

1995 ◽  
Vol 53 ◽  
pp. 210-211
Author(s):  
J. W. Mellowes ◽  
C. M. Chun ◽  
I. A. Aksay
Keyword(s):  
Amorphous Silica ◽  
Heterogeneous Nucleation ◽  
Homogeneous Nucleation ◽  
Silica Coating ◽  
Full Density ◽  
Optimal Conditions ◽  
Fine Grained ◽  
Alumina Particles ◽  
Complete Mullitization ◽  
Powder Compacts

Mullite (3Al2O32SiO2) can be fabricated by transient viscous sintering using composite particles which consist of inner cores of a-alumina and outer coatings of amorphous silica. Powder compacts prepared with these particles are sintered to almost full density at relatively low temperatures (~1300°C) and converted to dense, fine-grained mullite at higher temperatures (>1500°C) by reaction between the alumina core and the silica coating. In order to achieve complete mullitization, optimal conditions for coating alumina particles with amorphous silica must be achieved. Formation of amorphous silica can occur in solution (homogeneous nucleation) or on the surface of alumina (heterogeneous nucleation) depending on the degree of supersaturation of the solvent in which the particles are immersed. Successful coating of silica on alumina occurs when heterogeneous nucleation is promoted and homogeneous nucleation is suppressed. Therefore, one key to successful coating is an understanding of the factors such as pH and concentration that control silica nucleation in aqueous solutions. In the current work, we use TEM to determine the optimal conditions of this processing.

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