ChemInform Abstract: Benzenoid Hydrocarbon Aromaticity in Terms of Charge Density Descriptors

ChemInform ◽  
2010 ◽  
Vol 29 (9) ◽  
pp. no-no
Author(s):  
S. T. HOWARD ◽  
T. M. KRYGOWSKI
Keyword(s):  
Charge Density ◽  
Benzenoid Hydrocarbon

Benzenoid hydrocarbon aromaticity in terms of charge density descriptors

1997 ◽  
Vol 75 (9) ◽  
pp. 1174-1181 ◽  
Author(s):  
S.T. Howard ◽  
T.M. Krygowski
Keyword(s):  
Charge Density ◽  
Critical Point ◽  
Critical Points ◽  
Electron Distribution ◽  
Stationary Points ◽  
Bond Critical Point ◽  
Total Density ◽  
Benzenoid Hydrocarbon ◽  
Hartree Fock ◽  
Point Data

Hartree–Fock/6-31G** calculations on the benzenoid hydrocarbons benzene, naphthalene, phenanthrene, anthracene, pyrene, tetracene, triphenylene, chrysene, perylene, and coronene are used to investigate the link between aromaticity and the electron distribution. Topological charge density analysis is used, concentrating on the electron distribution ρ (and its Hessian) at bond and ring critical points. With regard to the bond critical point data, it is shown that ρc, [Formula: see text]ρc, and the bond "ellipticity" ε are closely correlated with the bond lengths so, as aromaticity indicators, they have little to add over and above existing indices based on structure. However, the same properties evaluated at the ring critical points in the total density, and also at the equivalent stationary points in the π and σ densities, correlate closely with two different aromaticity indices (one based on structure, the other on magnetic properties), the curvature of ρ perpendicular to the ring plane giving (marginally) the best results. Hence a ring critical point (RCP) index is proposed as a way of quantifying aromaticity, based directly on the electron distribution. Keywords: quantum chemistry, electron density, aromaticity, aromaticity index, HOMA, NICS.

Incommensurate modulated phases of the NbxTa1-xTe4 charge density wave system

1992 ◽  
Vol 50 (1) ◽  
pp. 58-59
Author(s):  
S. Ritchie ◽  
J. C. Bennett ◽  
A. Prodan ◽  
F.W. Boswell ◽  
J.M. Corbett
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Direct Evidence ◽  
Density Wave ◽  
Wave System ◽  
Modulated Phases ◽  
Metal Atoms ◽  
Incommensurate Modulation ◽  
End Members ◽  
Modulation Wave Vector

A continuous sequence of compounds having composition NbxTa1-xTe4; 0 ≤ x ≤ 1 have been studied by electron diffraction and microscopy. Previous studies have shown that the end members of the series, TaTε4 and NbTε4 possess a quasi-one-dimensional character and exhibit charge density wave (CDW) distortions. In these compounds, the subcell structure is tetragonal with axes (a × a × c) and consists of the metal atoms (Nb or Ta) centered within an extended antiprismatic cage of Te atoms. At room temperature, TaTε4 has a commensurate modulation structure with a 2a × 2a × 3c unit cell. In NbTε4, an incommensurate modulation with × ∼ 16c axes is observed. Preliminary studies of the mixed compounds NbxTα1-xTε4 showed a discontinuous jump of the modulation wave vector commensurate to incommensurate when the Nb dopant concentration x, exceeded x ≃ 0.3, In this paper, the nature of the compositional dependence of is studied in greater detail and evidence is presented for a stepwise variation of . This constitutes the first direct evidence for a Devil's staircase in CDW materials.

Wave Analysis of the Charge Density Wave Dynamics in the Molecular Conductor (Perylene)2Pt(mnt)2 (mnt=maleonitriledithiolate)

1995 ◽  
Vol 5 (5) ◽  
pp. 539-545 ◽  
Author(s):  
J. Dumas ◽  
N. Thirion ◽  
M. Almeida ◽  
E. B. Lopes ◽  
M. J. Matos ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Wave Analysis ◽  
Wave Dynamics ◽  
Molecular Conductor

Macroscopic quantum tunneling of charge density waves

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-161-Pr10-163
Author(s):  
H. Matsukawa ◽  
H. Miyake ◽  
M. Yumoto ◽  
H. Fukuyama
Keyword(s):  
Charge Density ◽  
Quantum Tunneling ◽  
Charge Density Waves ◽  
Density Waves ◽  
Macroscopic Quantum ◽  
Macroscopic Quantum Tunneling

Phase slip scaling relationship for the 59 K and 143 K charge-density-waves in NbSe3

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-129-Pr10-132 ◽  
Author(s):  
J. P. McCarten ◽  
T. C. Jones ◽  
X. Wu ◽  
J. H. Miller ◽  
I. Pirtle ◽  
...  
Keyword(s):  
Charge Density ◽  
Charge Density Waves ◽  
Phase Slip ◽  
Density Waves ◽  
Scaling Relationship

Transversely driven charge density waves in NbSe3

1999 ◽  
Vol 09 (PR10) ◽  
pp. Pr10-65-Pr10-67
Author(s):  
N. Markovic ◽  
M. A.H. Dohmen ◽  
H. S.J. van der Zant
Keyword(s):  
Charge Density ◽  
Charge Density Waves ◽  
Density Waves

Dynamical fluctuation of the site-charge density in metallic β″ -(BEDT-TTF)(TCNQ)

2004 ◽  
Vol 114 ◽  
pp. 149-151 ◽  
Author(s):  
Kyuya Yakushi ◽  
Mikio Uruichi ◽  
Hiroshi Yamamoto ◽  
Reizo Kato
Keyword(s):  
Charge Density ◽  
Dynamical Fluctuation

Tunneling spectroscopy in the Charge-Density Wave conductor NbSe3

2004 ◽  
Vol 114 ◽  
pp. 135-136 ◽  
Author(s):  
E. Slot ◽  
K. O'Neill ◽  
H. S.J. van der Zant ◽  
R. E. Thorne
Keyword(s):  
Charge Density ◽  
Charge Density Wave ◽  
Density Wave ◽  
Tunneling Spectroscopy
Sign in / Sign up

Export Citation Format

Share Document