Correlation in Molecules

Suba, S.; Whitehead, M. A.

doi:10.1142/9789812830586_0002

Cited by 4 publications

(3 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…A much better agreement is obtained with BSSE-corrected DFT calculations that predict the formation of only one hydrogen bond and only slightly different H (water) −O (surface) distances (1.81 Å and ∼3 Å) . These discrepancies must reflect the absence of self interaction corrections in DFT and improper treatment by the DFT functionals of the van der Waals (dispersion) attractive forces, arising from the long-range correlations of electronic density fluctuations, − which makes this technique less accurate than RHF/6-31G(d,p) in predicting hydrogen bonding and bridging. Furthermore, whereas DFT-GGA yields varying C−O bond lengths in CO 3 (1.29 to 1.37 Å), the RHF/6-31G(d,p) optimized C−O bond lengths agree with the bulk calcite bond lengths to within 1%.…”

Section: Discussionmentioning

confidence: 99%

Theoretical Insights into the Hydrated (10.4) Calcite Surface: Structure, Energetics, and Bonding Relationships

Villegas-Jiménez

Mucci²,

Whitehead³

2009

Langmuir

View full text Add to dashboard Cite

show abstract

Section: Discussionmentioning

confidence: 99%

Theoretical Insights into the Hydrated (10.4) Calcite Surface: Structure, Energetics, and Bonding Relationships

Villegas-Jiménez

Mucci²,

Whitehead³

2009

Langmuir

View full text Add to dashboard Cite

show abstract

“…Three such methods have been suggested: the use of Krieger-Li-Iafrate exchange correlation potentials, 41 the use of current-density functionals, 58 and the use of alternate density functional formalisms to Kohn-Sham theory. 42,43 Each has been advocated to improve just one of the four problems described, but since all four problems have a common fundamental cause, all three of these new methods may solve more than just the one problem it was conceived to cure. Hence, we look forward to a future in which DFT applications in molecular electronics may be routinely and confidently applied, but the present situation is far from this.…”

Section: Summary Directions and Alternativesmentioning

confidence: 99%

The Appropriateness of Density‐Functional Theory for the Calculation of Molecular Electronics Properties

Reimers

Cai

Bilić

et al. 2003

Annals of the New York Academy of Sciences

114

View full text Add to dashboard Cite

As molecular electronics advances, efficient and reliable computation procedures are required for the simulation of the atomic structures of actual devices, as well as for the prediction of their electronic properties. Density-functional theory (DFT) has had widespread success throughout chemistry and solid-state physics, and it offers the possibility of fulfilling these roles. In its modern form it is an empirically parameterized approach that cannot be extended toward exact solutions in a prescribed way, ab initio. Thus, it is essential that the weaknesses of the method be identified and likely shortcomings anticipated in advance. We consider four known systematic failures of modern DFT: dispersion, charge transfer, extended pi conjugation, and bond cleavage. Their ramifications for molecular electronics applications are outlined and we suggest that great care is required when using modern DFT to partition charge flow across electrode-molecule junctions, screen applied electric fields, position molecular orbitals with respect to electrode Fermi energies, and in evaluating the distance dependence of through-molecule conductivity. The causes of these difficulties are traced to errors inherent in the types of density functionals in common use, associated with their inability to treat very long-range electron correlation effects. Heuristic enhancements of modern DFT designed to eliminate individual problems are outlined, as are three new schemes that each represent significant departures from modern DFT implementations designed to provide a priori improvements in at least one and possible all problem areas. Finally, fully semiempirical schemes based on both Hartree-Fock and Kohn-Sham theory are described that, in the short term, offer the means to avoid the inherent problems of modern DFT and, in the long term, offer competitive accuracy at dramatically reduced computational costs.

show abstract

“…For the known approximate functionals, the exchange and correlation contributions are not properly balanced, and hence the self-energy terms are incorrectly represented. In most molecular or solid-state applications of Kohn-Sham DFT, this problem is of little consequence, and hence alternate DFT formalisms 52,53 (in which the self-energy is correctly represented independent of the functional) have not been widely pursued. The consequences are severe, however, if one attempts to remove an electron far from the atoms, with, for example, Kohn-Sham DFT calculations for ionization energies usually producing very good results if the energy of the cation is subtracted from that of the neutral, but very poor results if the electron is kept in the system and simply moved far from the molecule.…”

Section: Implications For Density Functional Calculations Of Through-mentioning

confidence: 99%

An Atomistic Approach to Conduction Between Nanoelectrodes Through a Single Molecule

Reimers

Shapley

Lambropoulos

et al. 2002

Annals of the New York Academy of Sciences

View full text Add to dashboard Cite

Capacitance and other properties of nanoelectrodes, finite-size metal clusters envisaged for use in complex molecular-electronic devices, are discussed. The applicability of classical electrostatics (Coulomb's and Gauss' law, Poisson's equation, etc.) to atomistic systems is investigated and the self-energy necessary to store a finite charge on an atom is found to be of central importance. In particular, the neglect of electron exchange is found to introduce severe limitations, with quantum calculations predicting fundamentally different electronic structures. Also, the well-known poor representation of the atomic self-energy inherent to modern DFT is discussed, along with its implications for molecular electronics calculations. An INDO/S method is introduced with new parameters for gold. This is the simplest approximate computational scheme that correctly includes quantum electrostatic, resonance, and spin effects, and is capable of describing arbitrary excited electronic states. Encouraging results are obtained for some trial problems. In particular, voltage differential between the electrodes in electrode-molecule-electrode conduction is obtained, not through an a priori prescription but rather by moving whole electrons between the electrodes and analyzing the response. The voltage drops across the molecule-electrode junctions and the central molecular region are then deduced. This alternative to the current Landauer-based 1-particle transmission equations for electrode-molecule-electrode conduction is discussed in terms of the use of the electronic states of the system. It provides a proper description not only of conduction via electrode-to-molecule charge or hole transfer but also of conduction via simultaneous charge and hole transfer via low-lying excited molecular electronic states, including the ability to account for electroluminescence and other chemical effects. In addition, various aspects of our research on the quantitative prediction of the I(V) curves for electrodemolecule-electrode conduction are reviewed, including demonstration of the equivalence of the formalisms generated by the Datta and the Mujica-Ratner groups, and the development of analytically solvable paradigms, including the conduction through a linear-chain Hückel wire.

show abstract

Correlation in Molecules

Cited by 4 publications

References 0 publications

Theoretical Insights into the Hydrated (10.4) Calcite Surface: Structure, Energetics, and Bonding Relationships

Theoretical Insights into the Hydrated (10.4) Calcite Surface: Structure, Energetics, and Bonding Relationships

The Appropriateness of Density‐Functional Theory for the Calculation of Molecular Electronics Properties

An Atomistic Approach to Conduction Between Nanoelectrodes Through a Single Molecule

Contact Info

Product

Resources

About