Energy gap of extended states in SiC-doped graphene nanoribbon: Ab initio calculations

2017 ◽  
Vol 400 ◽  
pp. 1-5 ◽  
Author(s):  
Xiaoshi Liu ◽  
Yong Wu ◽  
Zhongyao Li ◽  
Yong Gao
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Graphene Nanoribbon ◽  
Doped Graphene ◽  
Extended States

ab initio MO Optimization of Molecular Structures of Fluoro- and Chloro-Substituted Dibenzo-p-dioxines and the Effect of Halogen Substitution at the 2,3,7,8-Positions on Metabolic Attack

1997 ◽  
Vol 52 (11) ◽  
pp. 1418-1431 ◽  
Author(s):  
Roland Weber ◽  
Till Kühn ◽  
Hanspaul Hagenmaier ◽  
Günter Häfelinger
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Substituent Effects ◽  
Molecular Structures ◽  
X Ray ◽  
Degree Pattern ◽  
Chlorine Substituent ◽  
Homo Lumo ◽  
Good Agreement

Full ab initio optimizations were performed on the molecular structures of 24 fluorinated and chlorinated dibenzodioxines (PFDD/PCDD ) and dibenzofurans (PFDF/PCDF). Reasonable agreement was found by comparing the geometries of four calculated structures with known X-ray data from the literature. For the fluorine substituent, calculated electron densities (Mulliken total charges and π-electron charges) clearly demonstrate the opposite influence of the inductive (I) and mesomeric (M) effect. The changes in π-densities at carbons in ortho-, meta- and para-position are constant for each fluorine substituent (independent of degree, pattern, and position of substitution). It is thus possible to calculate the π-densities of the substituted dioxines by increments starting from dibenzodioxine. π-Charges from quantum mechanical calculations and the increment system show good agreement even for OctaFDD (O8FDD ), where eight substituent effects are acting additively. Compared with fluorine, the chlorine substituent exercises a smaller -I-effect and a clearly weaker +M-effect. The HOMO coefficients of the unsubstituted dibenzodioxine and dibenzofuran, extracted from ab initio calculations, yield a good explanation for the observed regioselective metabolic attack at the 2,3,7,8-positions. The squares of the HOMO-coefficients of the 2,3,7,8-positions in dibenzodioxine (DD ) are about ten times greater than those of the 1,4,6,9-positions. These HOMO coefficients are practically unaffected by halide substitution. But halogen substitution reduces strongly the electron density at the halogen-bound carbon, which, however, is a necessary prerequisite for the electrophilic oxygen transfer during metabolism. One would therefore expect halogen substitution of dibenzodioxine and dibenzofuran (DF) at the 2,3,7,8-position to hinder metabolism, as is indeed found. This provides a plausible explanation for the highly selective tissue retention of 2,3,7,8-substituted PCDDs and PCDFs. Our ab initio calculations of five tetra CDDs (T4CDDs) confirm the postulate of Kobayashi et al. [1 ] who, using semiempirical calculations, found a correlation between the toxicity of a dioxine congener and its absolute molecular hardness. The 2,3,7,8-T4CDD also exhibits the smallest absolute hardness (derived from the HOMO-LUMO energy gap) in our calculations.

Cluster Models of Doped Ionic Crystal Scintillators. Quantum Calculations+

1994 ◽  
Vol 348 ◽  
Author(s):  
M. Berrondo ◽  
J.F. Rivas-Silva ◽  
J.B. Czirr
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Ionic Crystal ◽  
Energy Gap ◽  
Alkali Halides ◽  
Alkali Cation ◽  
Quantum Calculations ◽  
Pure Crystal ◽  
Absorption And Emission ◽  
Quantum Electronic

ABSTRACTWe have performed quantum electronic ab initio calculations of clusters of alkali halides, both pure and doped. In order to estimate the pure crystal energy gap and the dopant excitation, we have considered a central cation and four shells of ions surrounding it. We have studied KC1, Nal, NaCl and KI, both pure and with a Tl+ ion replacing thecentral alkali cation. Encouraging results are presented for absorption and emission.

Dissociation of the COS+ ion by photoionisation: experiment and ab initio calculations The Franck-Condon energy gap an the vibronic state Franck-Condon energy regions

1996 ◽  
Vol 209 (2-3) ◽  
pp. 143-157 ◽  
Author(s):  
M.-J. Hubin-Franskin ◽  
J. Delwiche ◽  
P.-M. Guyon ◽  
M. Richard-Viard ◽  
M. Lavollée ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Vibronic State ◽  
Franck Condon

FREQUENCY-DEPENDENT HYPERPOLARIZABILITY OF BENZENE DERIVATIVES: AB-INITIO CALCULATIONS

2007 ◽  
Vol 16 (03) ◽  
pp. 367-380
Author(s):  
DIKSHA MAKWANI ◽  
R. VIJAYA
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Lone Pair ◽  
Benzene Derivatives ◽  
Structure Property ◽  
Disubstituted Benzene ◽  
Structure Property Relationship ◽  
Donor Acceptor ◽  
Acceptor Capacity

Structure–property relationship and dispersion effects for disubstituted benzene molecules have been investigated. Ab-initio calculations of the first hyperpolarizabilities (β) of donor–acceptor benzene derivatives show that the magnitude of β depends upon the availability of the lone pair of electrons on the nitrogen atom to conjugate with the benzene ring. The HOMO–LUMO energy gap and β have an inverse relationship. From the dispersion studies, it is observed that the first resonance peak shifts towards lower frequencies as the donor/acceptor capacity increases.

Calculation of Energy Levels of Cerium in Inorganic Scintillator Crystals

1994 ◽  
Vol 348 ◽  
Author(s):  
J. Andriessen ◽  
P. Dorenbos ◽  
C.W.E. van Eijk
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Energy Gap ◽  
Energy Levels ◽  
Fair Agreement ◽  
High Symmetry ◽  
Inorganic Scintillator ◽  
Low Symmetry

ABSTRACTFully relativistic ab initio calculations have been performed on energy levels of cerium in BaF2, LaF3, YAP and YAG. Also nonrelativistic calculations were done on cerium in LSO. The results are in fair agreement with experiment. Both the splitting of the 4f and 5d levels and the 4f–5d energy gap can be explained in the high symmetry crystal BaF2 as well as in the low symmetry crystals LaF3, YAP, YAG and LSO.

Millimetre-wave and infrared spectroscopy of Br13 CN: anharmonic force field of cyanogen bromide from spectroscopic data and ab initio calculations

1997 ◽  
Vol 90 (3) ◽  
pp. 495-497
Author(s):  
CLAUDIO ESPOSTI ◽  
FILIPPO TAMASSIA ◽  
CRISTINA PUZZARINI ◽  
RICCARDO TARRONI ◽  
ZDENEK ZELINGER
Keyword(s):  
Infrared Spectroscopy ◽  
Force Field ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Spectroscopic Data ◽  
Cyanogen Bromide ◽  
Millimetre Wave ◽  
Anharmonic Force
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