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.

INSULATOR-TO-METAL TRANSITION IN LaRhO3 UNDER HIGH PRESSURE

1995 ◽  
Vol 09 (11n12) ◽  
pp. 701-709 ◽  
Author(s):  
R. ASOKAMANI ◽  
CH. U.M. TRINADH ◽  
G. PARI ◽  
S. NATARAJAN
Keyword(s):  
High Pressures ◽  
Local Density ◽  
Tight Binding ◽  
Band Structure Calculations ◽  
Equilibrium Lattice Constant ◽  
Band Insulator ◽  
Lmto Method ◽  
A Charge ◽  
Structure Calculations ◽  
Cell Volumes

The band structure calculations of perovskite transition metal compound LaRhO 3 performed using 'tight binding linear muffin tin orbital' (TB-LMTO) method within local density approximation (LDA) under ambient and high pressures are reported here. Our calculations are able to successfully explain the insulating nature of the system and the insulator-to-metal transition (IMT) is observed for the reduced volume of 0.90. The first electronic structure calculation reported here for LaRhO 3 enables us to compare it with that of LaCoO 3 which brings out the role played by the d bands. These studies lead to distinguish between these two insulating systems and LaCoO 3 is found to be a charge transfer (CT) insulator which is in agreement with the recent experimental observations whereas LaRhO 3 is a conventional band insulator. Further, the equilibrium lattice constant, bulk modulus, its first derivative, and metallization volume obtained from the total energy calculations for expanded and reduced cell volumes are also reported for LaRhO 3.

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.

La3Ni4Al2: a new layered aluminide

2019 ◽  
Vol 234 (9) ◽  
pp. 581-586
Author(s):  
Nazar Zaremba ◽  
Yurij Schepilov ◽  
Galyna Nychyporuk ◽  
Viktor Hlukhyy ◽  
Volodymyr Pavlyuk
Keyword(s):  
Crystal Structure ◽  
Tight Binding ◽  
Orbital Method ◽  
Single Crystal Diffraction ◽  
Coordination Polyhedra ◽  
Atomic Sphere ◽  
X Ray ◽  
Square Prism ◽  
Sphere Approximation ◽  
Structure Calculations

Abstract The new ternary compound La3Ni4Al2 has been synthesized and the crystal structure has been studied by X-ray single crystal diffraction. La3Ni4Al2 is the first aluminide, crystallizing in the La3Ni4Ga2-type. The crystal structure of La3Ni4Al2 consists of La-layers and hetero-atomic Ni/Al layers, sequentially alternating along the a axis (pseudo-hexagonal c axis). According to electronic structure calculations using the tight-binding linear muffin-tin orbital method in the atomic-sphere approximation (TB-LMTO-ASA), strong Al–Ni interactions have been established. The coordination polyhedra for the Al atoms are cuboctahedra, whereas the bicapped square prism and bicapped square antiprism are typical for nickel atoms. The lanthanum atoms are enclosed in pseudo Frank–Kasper polyhedra.

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.

Electronic Energy Bands in γ-InSe with and without Intercalated Lithium

1990 ◽  
Vol 210 ◽  
Author(s):  
P. Gomes Da Costa ◽  
M. Balkanski ◽  
R. F. WALLIS
Keyword(s):  
Lithium Atom ◽  
Electronic Band Structure ◽  
Tight Binding ◽  
Electronic Energy ◽  
Band Gaps ◽  
Energy Bands ◽  
Energy Position ◽  
Electronic Band ◽  
Direct Band ◽  
Electronic Energy Bands

AbstractThe effect of intercalated lithium on the electronic band structure of the γ-polytype of InSe has been investigated using a tight-binding method. The energy bands of the pure polytype were calculated and the results compared with previous work. The modifications of the energy bands produced by the introduction of one lithium atom per unit cell were calculated for the lowest potential energy position of the lithium atom in the Van der Waals gap between layers. The results for the changes in the smallest and next-to-smallest direct band gaps are compared with experimental data. An interpretation of a photoluminescence peak produced by lithium intercalation is given.

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.

scholarly journals ATiO3 (A = Ca, Sr, Ba & BP) Pervoskites in Cubic and Tetragonal Phase using TB-LMTO-ASA Method

2019 ◽  
Vol 9 (2S2) ◽  
pp. 707-714
Keyword(s):  
Band Gap ◽  
Density Of States ◽  
Tetragonal Phase ◽  
Density Functional ◽  
Tight Binding ◽  
Partial Density ◽  
Cubic Phase ◽  
Lmto Method ◽  
Orbital Position ◽  
Sphere Approximation

Ground state properties of ATiO3 (A = Ca, Sr, Ba & Pb) pervoskite structures in cubic and tetragonal phase were studied by tight binding linear muffin-tin orbital (TB-LMTO) method in the framework of density functional theory (DFT) with the atomic-sphere approximation (ASA). The total energy of all the compounds come under the above said structures have shown that the cubic phase is the stable structure in the ambient condition. Among these pervoskites maximum bulk modulus was obtained for BaTiO3 . Direct (cubic) and indirect (tetragonal) band gap was observed from the band structure calculations and the values fall within the range of 1.5 – 1.7 eV. Electron distribution of each element in the valence and conduction bands was clearly obtained from the density of states (DOS) and partial density of states (PDOS) for all the compounds. The magnetization values were found in the range of 0.4 – 0.56 x 10-5µB. The‘d’ orbital position of Ti was observed for all the ABO3 compounds and shifted away from the Fermi level except for Ti in BaTiO3 . The refractive indices of the pervoskites were calculated from the energy band gap and the value is above 3 for all the compounds.

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.

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