First-Principles Study of Photoexcited Defects in Polysilane Chains

1990 ◽  
Vol 209 ◽  
Author(s):  
J. W. Mintmire ◽  
R. C. Mowrey ◽  
D. W. Brenner ◽  
B. I. Dunlap ◽  
C. T. White
Keyword(s):  
First Principles ◽  
Optical Materials ◽  
Density Functional ◽  
Model Simulation ◽  
Local Density ◽  
Density Functional Method ◽  
Functional Method ◽  
Charge Carriers ◽  
Bond Scission ◽  
Total Energies

ABSTRACTOrganopolysilane materials have recently demonstrated potential technological importance as positive photoresists, photoconductors, and nonlinear optical materials. Many of the technological applications of these materials depend intimately on the photoexcitation process in these materials, possibly resulting in either bond scission or the creation of mobile charge carriers. Herein we present some preliminary results of a model simulation of the photoexcitation process in oligomeric polysilane chains using a recently developed first-principles local-density functional method for the calculation of electronic structures,total energies, and gradients of the total energy with respect to nuclear coordinates.

Possidle Isomers and Electronic Structure of C60H36

1990 ◽  
Vol 206 ◽  
Author(s):  
B. I. Dunlap ◽  
D. W. Brenner ◽  
R. C. Mowrey ◽  
J. W. Mintmire ◽  
D. H. Robertson ◽  
...  
Keyword(s):  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Local Density ◽  
High Symmetry ◽  
Hydrogen Atoms ◽  
Functional Methods ◽  
Metastable Structure ◽  
Total Energies ◽  
Rice University

ABSTRACTNewly developed empirical hydrocarbon potentials and self-consistent first-principles local density functional methods are used to investigate possible isomers and the electronic structure of C60H36. Within the high symmetry Th structure conjectured by the groups at Rice University there are two inequivalent sets of hydrogen atoms containing twelve and twenty-four atoms respectively. Binding each set either inside or outside of the C60 cage leads to four isomers of C60H36 with inequivalent strain energies. Although we find that placing twelve hydrogens inside the cage can lead to a metastable structure, our calculated total energies suggest that the isomer with all the hydrogens on the outside of the cage is the energetically most stable.

Crystal Structure and Electronic Properties of Graphite-Like C7N Phase from First-Principles Calculations

2011 ◽  
Vol 268-270 ◽  
pp. 940-945
Author(s):  
Qian Ku Hu ◽  
Hai Yan Han ◽  
Hai Yan Wang ◽  
Qing Hua Wu
Keyword(s):  
Electronic Properties ◽  
First Principles ◽  
Density Functional ◽  
Hexagonal Boron Nitride ◽  
Density Functional Method ◽  
Functional Method ◽  
Stable Phase ◽  
Ambient Conditions ◽  
Electronic Band ◽  
Structural And Electronic Properties

The structural and electronic properties of graphite-like C7N compound have been calculated by using first-principles pseudopotential density functional method for ten possible C7N configurations, which are deduced from graphite and hexagonal boron nitride unit cell. The calculated total energy results show that the configuration C7N-I with AA stacking sequence along the c-axis based on hexagonal BN structure has been shown to be the most stable structure. From the calculated electronic band structures and electron density of states, the monolayer and bulk phase of C7N are expected to show insulating and metal states, respectively. The graphite-like C7N phases have been predicted to be a stable phase at ambient conditions by formation energy and elastic constant calculations. A critical pressure of about 41 GPa is expected for a synthesis of cubic C7N phase from this graphite-like C7N.

AN INVESTIGATION OF THE DOPING PROPERTIES OF ZnSe NANOCRYSTALS

2011 ◽  
Vol 25 (27) ◽  
pp. 3655-3662
Author(s):  
XIYING MA ◽  
JINWEI SONG
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Density Functional Method ◽  
Functional Method ◽  
Acceptor Impurity ◽  
Deep Acceptor ◽  
Deep Acceptor Level ◽  
P Type ◽  
Cl Atom ◽  
Znse Nanocrystals

This paper investigates the properties of ZnSe nanocrystals doped with single N , P or As atoms (for p-type doping) or single F , Cl or Br atoms (for n-type doping). The crystals are simulated using the local density functional method. Structures doped with an N or Cl atom remained symmetrical, but some distortion appeared with the other dopants. We found that N is the most efficient acceptor impurity for p-type doping, while Cl is the most suitable impurity for n-type doping. In the case of heavy p-type doping, complex defects such as N Se – Zn – V Se and N Se – Zn int easily form in the structure. We found that N Se – Zn – V Se produces a deep acceptor level in the bandgap, while N Se – Zn int produces a compensating donor level in p-type doping. The latter is the main reason for that p-type ZnSe is difficult to achieve. This study is useful to researchers investigating p- and n-type doping as well as device manufacturers.

Spatial Configurations of Molybdenum Atomic Chains

2011 ◽  
Vol 366 ◽  
pp. 447-450
Author(s):  
Han Xin Shen ◽  
Wen Zhang Zhu ◽  
Ai Yu Li
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Method ◽  
Functional Method ◽  
Electronic Energy ◽  
Energy Bands ◽  
Ladder Structure ◽  
Atomic Chains ◽  
Spatial Configurations ◽  
Electronic Energy Bands

The geometric and electronic structures of Molybdenum chains are studied by the first-principles of density-functional method. The present calculations reveal that Molybdenum can form planner chains in zigzag, dimer, and ladder structures. The most stable geometry is the Dimer structure chain. The ladder structure is found to be more stable than the zigzag one. Furthermore, the relative structural stability, the electronic energy bands, the density of states are discussed based on the ab initio calculations.

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