NOPR Collection:

Structure, stability and reactivity parameters of (CH)₈ isomers and their cation and anion radical counterparts : A theoretical study

2016-07-20T04:40:50Z

Title: Structure, stability and reactivity parameters of (CH)₈ isomers and their cation and anion radical counterparts : A theoretical study Authors: Priyakumar, U Deva; Sastry, G Narahari Abstract: Among the hydrocarbons with (CH)_2k (k = 1,2,3,4 .... ) structural formula. (CH)₈ where k=4, possesses nineteen local minima at semiempirical level with comparable heats of formation. AM1 procedure is found to be better than MNDO and PM3 in evaluating the heats of formation and geometries based on comparison with available experimental data of the neutral isomers. Vertical and adiabatic electron affinities and ionization potentials have been calculated for all the available isomers. The relative energy ordering is mainly controlled by the electronic factors rather than the strain. Koopman's theorem is not expected to yield reliable answers for ionization potentials, as the orbital relaxation seems to be very high for some isomers. The major geometric distortions are due to either Jahn-Teller distortions or strong vibronic interactions and the consequent reordering of the skeleton. Relaxation energies from vertical to adiabatic states are roughly proportional to the geometric deformations that occur upon ionization or addition of an electron. Page(s): 92-99

A density functional calculation of Ar⁺⁺(3s²3p³nl) satellite states

2016-07-20T04:38:41Z

Title: A density functional calculation of Ar⁺⁺(3s²3p³nl) satellite states Authors: Vikas; Roy, Amlan K; Deb, B M Abstract: The correlation states (satellites) of atoms, particularly of charged ions, are difficult to compute accurately. In this work, we present and discuss the results of Ar⁺⁺(3s²3p³nl) satellite states, calculated by employing a simple density-functional formalism within a single determinantal approach along with Slater's sum rule. A Kohn-Sham-type differential equation is solved numerically by employing the work-function-based potential of Harbola and Sahni for exchange while for correlation, the effects of two different correlation energy functionals (local Wigner and nonlocal Lee-Yang-Parr) have been studied. In some cases, Lee- Yang-Parr functional gives better results, while for others Wigner functional turns out to be better. About forty states are reported for the first time. Page(s): 32-39

Molecular dynamics study of the solid state photoreactivity of 3- and 4-cyano-trans-cinnamic acids

2016-07-20T04:49:01Z

Title: Molecular dynamics study of the solid state photoreactivity of 3- and 4-cyano-trans-cinnamic acids Authors: Sarma, Jagarlapudi A R P; Chaudhuri, Barnali; Desiraju, Gautam R Abstract: Molecular dynamics (MD) simulation studies show the importance of molecular motion and optimal π-π overlap of incipient reactive double bunds in the topochemical photodimerisation reactions of 3- and 4-cyanocinnamic acids. These simulations have been carried out in minicrystals consisting of 180 molecules and confirm earlier conclusions arising from packing calculations of static structures. A two-step diradical pathway for the climerisation is possible. A stepwise MD study has also been performed in which two molecules at the centres of the minicrystals have been dimerised and these calculations reveal the importance of thermal motion in these solid state photochemical reactions. Page(s): 253-261

Theoretical investigation of the electronic structure of molecules involved in green-plant photosynthesis

2016-07-20T04:34:12Z

Title: Theoretical investigation of the electronic structure of molecules involved in green-plant photosynthesis Authors: Datta, Sambhu N; Jha, Abhishek Abstract: Some of the advances made in our theoretical understanding of the Z scheme of photosynthesis in green plants are reviewed here. The Z-scheme embodies a sequence of light-activated, and very fast, electron transfer processes. The molecules under consideration belong to the central diagonal arm of the Z-scheme. These are plastoquinone-histidine complexes Q_I and Q_II’ plastoquinones (PQ), cytochrome-f, and Rieske protein. The electronic structures of these species have been investigated by semiempirical quantum chemical methods — CNDO/2 and INDO. In one case, the rate of electron transfer (from Q to Q and from Q to Q) has been theoretically determined. Results of these investigations serve in two ways. On the one hand, theoretical calculations confirm the observed redox potentials, and the rate of electron transfer. On the other hand, a set of fascinating information can be obtained, which clarifies several ideas about the structure, function and placement of these biological molecules in the condensed phase of chloroplast. Page(s): 120-131

NOPR Collection:

Structure, stability and reactivity parameters of (CH)8 isomers and their cation and anion radical counterparts : A theoretical study

A density functional calculation of Ar++(3s23p3nl) satellite states

Molecular dynamics study of the solid state photoreactivity of 3- and 4-cyano-trans-cinnamic acids

Theoretical investigation of the electronic structure of molecules involved in green-plant photosynthesis

Structure, stability and reactivity parameters of (CH)₈ isomers and their cation and anion radical counterparts : A theoretical study

A density functional calculation of Ar⁺⁺(3s²3p³nl) satellite states