Electronic Structure and Associated Optical Properties of LAPO4:Ce

1994 ◽  
Vol 348 ◽  
Author(s):  
K. C. Mishra ◽  
K. H. Johnson
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Green Emission ◽  
Scattered Wave ◽  
Cluster Approach ◽  
Small Magnitude ◽  
Lanthanum Phosphate ◽  
Consistent Field ◽  
Self Consistent Field ◽  
Good Agreement

ABSTRACTLanthanum phosphate activated by cerium and terbium is a well known lamp phosphor which is used for its green emission. In this paper, we have investigated the electronic structure and associated optical properties of lanthanum phosphate doped with cerium using the self consistent field scattered wave molecular orbital cluster approach. Relativistic corrections are included for the lanthanum and cerium centered clusters. In spite of the small magnitude of crystal field splitting, a significant admixture of the f-like orbitals with the ligand orbitals is observed for cerium. The optical transitions are calculated using the transition state formalism. The absorption peaks due to electronic transition from the f-like states to d-like states of cerium are found to be 271 rim, 259 nm, 245 nm, 208 nm and 194 nm which are in good agreement with the experiment. The nature of the band gap transition in lanthanum phosphate is also discussed.

Electronic Structure of Grain Boundaries and Interfaces in Polycrystalline Zinc Oxide

1981 ◽  
Vol 5 ◽  
Author(s):  
M. H. Sukkar ◽  
H. L. Tuller ◽  
K. H. Johnson
Keyword(s):  
Electronic Structure ◽  
Grain Boundaries ◽  
Scattered Wave ◽  
Theoretical Models ◽  
Interface States ◽  
Molecular Orbital Calculations ◽  
Conduction Bands ◽  
Consistent Field ◽  
Self Consistent Field ◽  
Zno Varistors

ABSTRACTPreliminary theoretical models for the electronic structure of grain boundaries and interfaces in polycrystalline ZnO have been constructed on the basis of self-consistent-field X-alpha scattered-wave (SCF-Xα-SW) cluster molecular-orbital calculations. The disposition and character of the interface states, relative to the valence and conduction bands of the otherwise perfect crystalline material, have been studied for clusters representing coordinatively unsaturated Zn surface sites and molecular O2 chemisorption thereon. The possible effects of the resuiting interface states on electron transport at grain boundaries in ZnO varistors have been addressed.

ELECTRONIC STRUCTURE AND OPTICAL PROPERTIES OF CRYSTALLINE C60

1992 ◽  
Vol 06 (06) ◽  
pp. 309-321 ◽  
Author(s):  
W.Y. CHING ◽  
MING-ZHU HUANG ◽  
YONG-NIAN XU ◽  
FANQI GAN
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Optical Spectrum ◽  
Local Density ◽  
Low Dielectric Constant ◽  
Experimental Measurements ◽  
Absorption Bands ◽  
Low Dielectric ◽  
Good Agreement

The electronic structure and optical properties of crystalline C 60 and their pressure dependence have been studied by first-principles local density calculations. It is shown that fcc C 60 has a low dielectric constant and an optical spectrum rich in structures. The spectrum shows five disconnected absorption bands in the 1.4 to 7.0 eV region with sharp structures in each band that can be attributed to critical point transitions. This is a manifestation of the localized molecular structure coupled with long range crystalline order unique to the C 60 crystal. At a sufficient high pressure, the structures in the optical spectrum start to merge due to the merging of the bands. These results are in good agreement with some recent experimental measurements.

Angle-Resolved Photoemission Extended Fine Structure Study Of Chemisorbed c(2×2)P/Fe(100): Comparison With Self-Consistent-Field Xα Scattered Wave Calculations

1996 ◽  
Vol 437 ◽  
Author(s):  
W.R.A. Huff ◽  
Y. Chen ◽  
X.S. Zhang ◽  
L.J. Terminello ◽  
F.M. Tao ◽  
...  
Keyword(s):  
Fine Structure ◽  
Linear Prediction ◽  
Spherical Wave ◽  
Scattered Wave ◽  
Interlayer Spacing ◽  
Structure Study ◽  
Consistent Field ◽  
Close Analysis ◽  
Self Consistent ◽  
Self Consistent Field

AbstractAngle-resolved photoemission extended fine structure (ARPEFS) was used to determine the structure of c(2×2)P/Fe(100) for the first time. P 1s core-level photoemission data were collected normal to the (100) surface and 45° off-normal along the [011] direction at room temperature. A close analysis of the auto-regressive linear prediction based Fourier transform and multiple-scattering spherical-wave calculations indicate that the P atoms adsorb in the high-coordination four-fold hollow sites. The P atoms bond 1.02 Å above the first layer of Fe atoms and the Fe-P-Fe bond angle is 140.6°. Additionally, it was determined that there is no expansion of the Fe surface. Self-consistent-field Xα scattered wave calculations were performed for the c(2×2)P/Fe(100) and the c(2×2)S/Fe(100) systems. These independent results are in excellent agreement with this P/Fe structure and the S/Fe structure previously published, confirming the ARPEFS determination that the Fe1-Fe2 interlayer spacing is contracted from the bulk value for S/Fe but not for P/Fe.

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