On the direct determination of constrained pure state one-electron density matrices: Part I. A new theoretical model for closed-shell systems

Das, Kalyan Kumar; Khan, Priyotosh; Bhattacharyya, S. P.

doi:10.1007/bf02847672

Cited by 7 publications

(1 citation statement)

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“…Microscopic approaches of handling such problems are, however, scarce. We feel, a constrained variational [3][4][5][6] approach in which energy is minimized subject to the satisfaction of one or more property constraints can theoretically provide useful clues for designing molecular chromophores for a particular purpose. As a specific case, we may focus on the designing of low band gap organic materials.…”

Section: Introductionmentioning

confidence: 99%

A constrained variational approach to the designing of low transport band gap materials: A multiobjective random mutation hill climbing method

Sarkar

Sharma

Bhattacharyya

2011

Int J of Quantum Chemistry

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Neutral polythiophene (PT) and polyselenophene (PSe) are semiconductors with band gaps of about 2 eV. We have proposed and implemented a constrained variational method in which total energy of neutral PT or PSe oligomers is minimized under the constraint that the band gap measured by HOMO-LUMO energy difference is also a minimum in each case. The constrained (bimodal) minimization has been carried out by an adaptive random mutation hill climbing method within the basic framework of Su-Schrieffer-Heeger type of model. We show that the "band-gap constrained minimization" automatically creates electron deficient quinoid regions (QR) in the PT or PSe chains, embedded in aromatic regions (ARs), on both sides. We have investigated how the number and distribution of such QRs can reduce the band gap. Band gap constrained electronic structure calculations thus provide designing clues for low transport band gap materials based on molecular chromophores.

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Section: Introductionmentioning

confidence: 99%