scholarly journals Theoretical and Experimental Studies on the C15 Intermetallic Compound NbCr2

1994 ◽  
Vol 364 ◽  
Author(s):  
F. Chu ◽  
D. J. Thoma ◽  
Y. He ◽  
T. E. Mitchell ◽  
S. P. Chen ◽  
...  
Keyword(s):  
Total Energy ◽  
Elastic Moduli ◽  
Experimental Studies ◽  
Atomic Sphere ◽  
Solubility Range ◽  
Volume Curve ◽  
Lmto Method ◽  
Sphere Approximation ◽  
Structure Density ◽  
Theoretical Results

AbstractThe electronic structure and total energy of the C15 NbCr2 phase have been calculated using the linear muffin-tin orbital (LMTO) method with the atomic sphere approximation (ASA). The total energy vs. volume curve, band structure, density of states and Fermi surface were obtained. The calculated results were used to examine several features of the C15 phase, including the elastic properties, phase formation and stability, and solubility range of the C15 phase. The theoretical results are compared to experimental studies on NbCr2 For example, the elastic moduli, phase stability, and homogeneity range have been determined with a variety of experimental techniques. Comparison of the experimental and theoretical results will be discussed.

Tuning of Energy Band Gaps in Ternary Semiconductors

2007 ◽  
Vol 31 ◽  
pp. 164-166 ◽  
Author(s):  
Rita John
Keyword(s):  
High Pressures ◽  
Tight Binding ◽  
Band Gaps ◽  
First Principle ◽  
Pressure Derivative ◽  
Atomic Sphere ◽  
Lmto Method ◽  
Direct Band ◽  
Sphere Approximation ◽  
Ternary Semiconductors

The first principle investigations on electronic structure of ABC2 (A = Cd; B = Si, Ge, Sn; C= P, As) pnictides using the Tight Binding Linear Muffin Tin Orbital (TB-LMTO) method within the Atomic Sphere Approximation (ASA) is reported. Variation of Eg with pressure reveals the direct and pseudodirect natures of these compounds. CdSiP2 shows a pseudo direct and CdGeP2, CdSnP2, CdSiAs2, CdGeAs2 and CdSnAs2 show direct band gap natures. Semiconductor to metal transition at high pressures is observed. Metallisation volumes (V/Vo) m and pressures (Pm), bulk modulus (Bo) and its pressure derivative (Bo 1) are reported. Correlation connecting Bo and the unit cell volume (Vo) is established.

Electronic Structure and Energetics of LaNi5, α-La2Ni10H and β-La2Ni10H14

1998 ◽  
Vol 513 ◽  
Author(s):  
H. Nakamura ◽  
D. Nguyen-Manh ◽  
D. G. Pettifor
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Charge Density ◽  
Tight Binding ◽  
Site Occupancy ◽  
Heat Of Formation ◽  
Hydrogen Atoms ◽  
Atomic Sphere ◽  
Sphere Approximation ◽  
Atomic Sphere Approximation

ABSTRACTThe electronic structure and energetics of LaNi5, its hydrogen solution (α-La2Ni10H) and its hydride (β-La2Ni10H14) were investigated by means of the tight-binding linear muffin-tin orbitals method within the atomic sphere approximation (TB-LMTO-ASA). Preferred site occupancy by the absorbed hydrogen atoms was investigated in terms of the charge density of the interstitial sites and the total energy, both of which indicate that the 6m site in the P6/mmm symmetry is the most preferred. A negative heat of formation of La2Ni10H14 was obtained from the total energy calculations.

Effect of Substitutions at the Nickel Site on the Electronic Structure of LaNi5 and its Hydrides

1998 ◽  
Vol 513 ◽  
Author(s):  
M. Gupta
Keyword(s):  
Electronic Structure ◽  
P Element ◽  
Atomic Sphere ◽  
P Elements ◽  
Self Consistent ◽  
Lmto Method ◽  
Sphere Approximation ◽  
Ni Substitution ◽  
Atomic Sphere Approximation ◽  
The Stability

ABSTRACTThe effect of Ni substitution in LaNi5 by 3d and s-p elements on the electronic structure of the intermetallic and its hydrides has been investigated using the self consistent linear muffin tin orbital (LMTO) method in the atomic sphere approximation (ASA). The Fermi level, EF, of LaNi4M (M = Fe,Co,Mn) is found to lie in the narrow additional M 3d subband above the Ni d states, leading to an increase in the density of states (DOS) at EF. In contrast, the substitution of Ni by an s element of the 3d series, Cu, or by an s-p element: Al or Sn results in a progressive filling of the Ni-d bands and in a decrease of the DOS at EF. In all the substituted intermetallic compounds, we find that the lattice expansion accounts for less than 50% of the observed decreased stability, this shows the importance of the effect of chemical substitution. We also discuss the factors which affect the electronic structure and the stability of the hydrides and compare our results with available experimental data.

Electronic Structure and Magnetic Properties of Transition Metal Doped Silicon Carbide

2001 ◽  
Vol 690 ◽  
Author(s):  
M. S. Miao ◽  
Walter R. L. Lambrecht
Keyword(s):  
Silicon Carbide ◽  
Magnetic Properties ◽  
Density Functional ◽  
Magnetic Behavior ◽  
Antiferromagnetic Coupling ◽  
Ferromagnetic Coupling ◽  
Atomic Sphere ◽  
Lmto Method ◽  
Sphere Approximation ◽  
Metal Doped

ABSTRACTThe magnetic properties of cubic (3C) silicon carbide (SiC) doped by first row transition metals (TM) are studied within the local spin density functional approach using the linearized muffin-tin orbital (LMTO) method in the atomic sphere approximation (ASA). The magnetic properties are found to depend strongly on the doping site. For the preferred doping site (Si), Cr and Mn exhibit the most pronounced magnetic behavior with Cr favoring ferromagnetic coupling and Mn antiferromagnetic coupling.

Ground State Properties of the Ai-Ti System

1990 ◽  
Vol 186 ◽  
Author(s):  
Prabhakar P. Singh ◽  
Mark Asta ◽  
Didier deFontaine ◽  
Mark van Schilfgaarde
Keyword(s):  
Ground State ◽  
Complete Agreement ◽  
Full Potential ◽  
Atomic Sphere ◽  
Lattice Constants ◽  
Ground State Properties ◽  
Lmto Method ◽  
Sphere Approximation ◽  
Atomic Sphere Approximation ◽  
Low Symmetry

AbstractGround state structural energies and lattice constants of Al-Ti system have been studied using the linear muffin-tin orbital (LMTO) method. In particular, we examine the effects of various approximations for the potential on the structural energies of low-symmetry compounds such as Al3Ti. In order to stabilize Al3Ti, in the atomic sphere approximation, the Muffin-Tin correction is essential although the resulting c/a is 10% too large. The lattice constants calculated with the full-potential LMTO method are in complete agreement with experiments, indicating the importance of non-sphericity of the potential for low-symmetry systems.

FIRST-PRINCIPLES CALCULATION OF THE MAGNETOCRYSTALLINE ANISOTROPY ENERGY FOR THE PSEUDOBINARY COMPOUND Y(Co1−xFex)5

1993 ◽  
Vol 07 (01n03) ◽  
pp. 745-748 ◽  
Author(s):  
JOAKIM TRYGG ◽  
LARS NORDSTRÖM ◽  
BÖRJE JOHANSSON
Keyword(s):  
Magnetocrystalline Anisotropy ◽  
Energy Difference ◽  
Anomalous Behavior ◽  
Anisotropy Energy ◽  
First Principles Calculation ◽  
Atomic Sphere ◽  
Lmto Method ◽  
Sphere Approximation ◽  
Total Energy Difference ◽  
Magnetocrystalline Anisotropy Energy

From the experimental behavior of the magnetocrystalline anisotropy energies of the pseudobinary compounds Y(Co1−xFex)5, it has been argued that the magnetocrystalline anisotropy energies for YCo5 and the hypothetical compound YFe5 will have different signs. This anomalous behavior is attributed to the change of the number of 3d electrons and their orbital moments when proceeding from YFe5 to YCo5. The magnetocrystalline anisotropy energies are calculated using the linear muffin-tin orbital (LMTO) method in the atomic sphere approximation (ASA) including spin-orbit interaction and orbital polarization. The force-theorem is used to express the total energy difference (between the two directions of magnetization) as a difference in the sum of the single particle eigenvalues. We find that it is possible to predict the correct easy-axis for YCo5 and YFe5. Secondly it is found that the inclusion of orbital polarization is essential for the cobalt compound but less important for the iron compound. The different contributions from the two inequivalent transition metal sites to the anisotropy energy and orbital magnetization are discussed.

Study of a Vibratory Feeder with Repulsive Surface Which Has Directional Characteristic

1980 ◽  
Vol 102 (1) ◽  
pp. 94-101 ◽  
Author(s):  
S. Okabe ◽  
Y. Yokoyama
Keyword(s):  
Experimental Studies ◽  
Directional Characteristic ◽  
Vibratory Feeder ◽  
The Mean ◽  
Theoretical Results

This paper treats the motion of a particle on a vibratory feeder whose track has directional characteristic in repulsive motion, for examples, obliquely bristled track, obliquely sliced track and so on. Under some assumptions, the practical equation for predicting the mean conveying velocity is shown and the relations between conveying condition and the mean conveying velocity are clarified theoretically. These relations are shown in various diagrams. Referring these diagrams, the optimum conveying conditions are discussed also. The theoretical results show that the mean conveying velocity is considerably larger than that of the ordinary feeder. The theoretical results are confirmed by experimental studies.

Pneumatic Mechanism of Gas Cooled or Heated Through a Throttle Orifice

2011 ◽  
Vol 141 ◽  
pp. 408-412 ◽  
Author(s):  
Yao Bao Yin ◽  
Ling Li
Keyword(s):  
Equation Of State ◽  
Total Energy ◽  
Negative Energy ◽  
Experimental Results ◽  
Attractive Force ◽  
Positive Energy ◽  
Real Gas ◽  
Thomson Coefficient ◽  
Theoretical Results ◽  
Conversion Temperature

The mechanism of gas cooled or heated through a pneumatic throttle orifice is analyzed. Supposing the total energy of the gas is constant, if the force between the molecules does positive energy, it makes gas heated; if it does negative energy, it makes gas cooled. The conversion temperature of gas is an evaluation parameter for repulsive or attractive force. It has utilized Joule-Thomson coefficient and real gas equation of state to obtain the characteristics of conversion temperature, and the relationships between the molecules distance and the phenomenon of gas cooled or heated after throttle at normal temperature by the conversion characteristics are achieved. The experimental results agreed well with the theoretical results.

Total Energy and Force Calculations with the LMTO Method

1989 ◽  
pp. 1-13 ◽  
Author(s):  
O. K. Andersen ◽  
M. Methfessel ◽  
C. O. Rodriguez ◽  
P. Blöchl ◽  
H. M. Polatoglou
Keyword(s):  
Total Energy ◽  
Lmto Method

scholarly journals MHD-waves in the geomagnetic tail: A review

10.12737/7168 ◽  
2015 ◽  
Vol 1 (1) ◽  
pp. 4-22 ◽  
Author(s):  
Анатолий Леонович ◽  
Anatoliy Leonovich ◽  
Виталий Мазур ◽  
Vitaliy Mazur ◽  
Даниил Козлов ◽  
...  
Keyword(s):  
Numerical Models ◽  
Experimental Studies ◽  
Low Frequency ◽  
Detailed Comparison ◽  
Mhd Waves ◽  
Theoretical Studies ◽  
Geomagnetic Tail ◽  
Magnetopause Oscillations ◽  
Experimental And Theoretical Studies ◽  
Theoretical Results

This article presents the review of experimental and theoretical studies on ultra-low-frequency MHD oscillations of the geomagnetic tail. We consider the Kelvin–Helmholtz instability at the magnetopause, oscillations with a discrete spectrum in the “magic frequencies” range, the ballooning instability of coupled Alfvén and slow magnetosonic waves, and “flapping” oscillations of the current sheet of the geomagnetic tail. Over the last decade, observations from THEMIS, CLUSTER and Double Star satellites have been of great importance for experimental studies. The use of several spacecraft allows us to study the structure of MHD oscillations with high spatial resolution. Due to this, we can make a detailed comparison between theoretical results and those obtained from multi-spacecraft studies. To make such comparisons in theoretical studies, in turn, we have to use the numerical models closest to the real magnetosphere.

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