Computing the Position-Spread tensor in the CAS-SCF formalism

Khatib, Muammar El; Leininger, Thierry; Bendazzoli, Gian Luigi; Evangelisti, Stefano

doi:10.1016/j.cplett.2013.10.080

Cited by 16 publications

(19 citation statements)

References 23 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…To this purpose, it is possible to investigate the response of the system to the action of electric fields along a direction parallel to the tube axis. A further possibility is given by the use of the formalism of the so-called Localization Tensor [48][49][50][51][52], or Second Moment Cumulant of the Position operator, for which an implementation at CAS-SCF level has recently been achieved in our group [53].…”

Section: Statementioning

confidence: 99%

The Electronic Structure of Short Carbon Nanotubes: The Effects of Correlation

Chilkuri

Evangelisti

Leininger

et al. 2015

Advances in Condensed Matter Physics

Self Cite

View full text Add to dashboard Cite

This paper presents atight bindingandab initiostudy of finite zig-zag nanotubes of various diameters and lengths. The vertical energy spectra of such nanotubes are presented, as well as their spin multiplicities. The calculations performed using thetight bindingapproach show the existence of quasi-degenerate orbitals located around the Fermi level, thus suggesting the importance of high-qualityab initiomethods, capable of a correct description of the nondynamical correlation. Such approaches (Complete Active Space SCF and Multireference Perturbation Theory calculations) were used in order to get accurate ground and nearest excited-state energies, along with the corresponding spin multiplicities.

show abstract

Section: Statementioning

confidence: 99%

The Electronic Structure of Short Carbon Nanotubes: The Effects of Correlation

Chilkuri

Evangelisti

Leininger

et al. 2015

Advances in Condensed Matter Physics

Self Cite

View full text Add to dashboard Cite

show abstract

“…In Figure , the axial component of the TPS (as implemented in MOLPRO) computed using a double‐ζ atomic natural orbital basis set with polarization functions (ANO‐DZP) is depicted as function of the system size. Although the predicted linear behavior of Λ zz is an asymptotic limit, already for the first (even‐numbered) [ n ]cyclacenes, a clear linear trend is observed with a fully quantum mechanical approach, thus supporting the tight‐binding results.…”

Section: The Total Position Spread and Polarizability Tensorsmentioning

confidence: 99%

A theoretical study on cyclacenes: Analytical tight‐binding approach

Battaglia

Bendazzoli

et al. 2018

Int J of Quantum Chemistry

Self Cite

View full text Add to dashboard Cite

We present a theoretical study of cyclacene molecules performed at tight-binding level. The orbital energies and eigenvectors have been analytically computed, and exact expressions for the axial component of the total position spread and polarizability tensors have been obtained. In absence of dimerization, the system has a D nh symmetry, where n is the number of hexagonal units. The energy bands present no gap at the Fermi level, and to this fact it corresponds a diverging (perelectron) polarizability for n ! 1 in the direction of the system symmetry axis. The two (degenerate) components of the polarizability on the r h symmetry plane, conversely, remain finite for n ! 1. The total position spread tensor presents a qualitatively different behavior, since all the three components of the position spread per electron remain finite for n ! 1. The results are analyzed and discussed for both axial and planar components separately as these are affected differently with respect to the increasing system size. Both dipole polarizability and total position spread have been computed using an ab initio approach for the smallest systems, to compare the analytical tight-binding expressions with a higher-level theory. K E Y W O R D Scomplete active space self-consistent field, cyclacenes, polarizability, tight-binding, total position spread 1 | I N TR ODU C TI ON First imagined by Edgar Heilbronner in 1954, [1] [n]cyclacenes (cyclic polyacenes) have been a fascinating research topic. A thorough understanding of cyclacenes is important as they could be considered as the shortest zigzag carbon nanotube (CNT) and could be used to model finite-length CNTs in simulations. Furthermore, [n]cyclacene chains have the potential to be used as precursors for the synthesis of zigzag CNTs, allowing for a more controlled way to fabricate this type of carbon nanostructure. [2] Unfortunately, the synthesis of [n]cyclacenes has not yet been realized as it is summarized in a number of reviews. [3][4][5] Besides experimental work on [n]cyclacenes, several computational studies using semi-empirical methods [6][7][8][9][10][11][12][13][14][15][16] and ab initio methods [17][18][19][20][21][22] have been carried out on these systems. The semi-empirical work was focused both on an analysis of the structural properties of the cyclacenes as well as the behavior of electronic properties such as the HOMO-LUMO gap as a function of the system size parameter n. It was found that the gap decreases in an alternating way depending on the parity of n, as more units are added to the system. Depending on the type of semi-empirical Int J Quantum Chem. 2018;118:e25569.

show abstract

“…Possible applications of PST to the chemical bonding in molecules were given in Refs. . An important contribution was also been made by Ángyán and coworker who attempted to relate several known chemical localization descriptors to the density response function and to construct spatially resolved analog of PST.…”

Section: Introductionmentioning

confidence: 99%

Spatially resolved characterization of electron localization and delocalization in molecules: Extending the Kohn‐Resta approach

Astakhov

Tsirelson

2018

Int J of Quantum Chemistry

View full text Add to dashboard Cite

In this work, the electron organization of many‐electron systems is considered in a context of the linear response theory extending the Kohn‐Resta view on electron localization phenomenon. The variances of the local electronic position and momentum operators are linked via the fluctuation‐dissipation theorem to the optical conductivity tensor, that is, to observable spectroscopic properties. It is demonstrated that the electron position variance density quantifies a degree of electron delocalization in each point of position space and distinguishes between metallic and insulating character of electronic states. The momentum variance density estimates a degree of electron localization and is immediately related to electronic kinetic energy density in the Ghosh‐Berkowitz‐Parr form giving a physical interpretation to the later. We show that electron localization and delocalization phenomena in atoms and molecules can be probed by external electric field. This approach provides new electronic descriptors distinguishing and quantifying chemical bonds of different types.

show abstract

Computing the Position-Spread tensor in the CAS-SCF formalism

Cited by 16 publications

References 23 publications

The Electronic Structure of Short Carbon Nanotubes: The Effects of Correlation

The Electronic Structure of Short Carbon Nanotubes: The Effects of Correlation

A theoretical study on cyclacenes: Analytical tight‐binding approach

Spatially resolved characterization of electron localization and delocalization in molecules: Extending the Kohn‐Resta approach

Contact Info

Product

Resources

About