Model, Multiply Hydrogen-Bonded Water Oligomers (N= 3−20). How Closely Can a Separable, ab Initio-Grounded Molecular Mechanics Procedure Reproduce the Results of Supermolecule Quantum Chemical Computations?

1997 ◽  
Vol 101 (46) ◽  
pp. 8680-8694 ◽  
Author(s):  
Nohad Gresh
Keyword(s):  
Ab Initio ◽  
Molecular Mechanics ◽  
Quantum Chemical ◽  
Quantum Chemical Computations ◽  
Hydrogen Bonded

Excitons in poly(para phenylene vinylene): a quantum-chemical perspective based on high-level ab initio calculations

2016 ◽  
Vol 18 (4) ◽  
pp. 2548-2563 ◽  
Author(s):  
Stefanie A. Mewes ◽  
Jan-Michael Mewes ◽  
Andreas Dreuw ◽  
Felix Plasser
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Quantum Chemical ◽  
Phenylene Vinylene ◽  
High Level ◽  
Quantum Chemical Computations

Exciton analyses of high-level quantum-chemical computations for poly(paraphenylene vinylene) reveal the nature of the excitonic bands in PPV oligomers.

Computational Photobiology and Beyond

2010 ◽  
Vol 63 (3) ◽  
pp. 413 ◽  
Author(s):  
Igor Schapiro ◽  
Mikhail N. Ryazantsev ◽  
Wan Jian Ding ◽  
Mark M. Huntress ◽  
Federico Melaccio ◽  
...  
Keyword(s):  
Quantum Mechanics ◽  
Excited State ◽  
Ab Initio ◽  
Molecular Mechanics ◽  
Chemical Treatment ◽  
Quantum Chemical ◽  
Organic Molecules ◽  
Molecular Devices ◽  
Computational Studies ◽  
Computational Investigation

In this paper we review the results of a group of computational studies of the spectroscopy and photochemistry of light-responsive proteins. We focus on the use of quantum mechanics/molecular mechanics protocols based on a multiconfigurational quantum chemical treatment. More specifically, we discuss the use, limitations, and application of the ab initio CASPT2//CASSCF protocol that, presently, constitutes the method of choice for the investigation of excited state organic molecules, most notably, biological chromophores and fluorophores. At the end of this Review we will also see how the computational investigation of the visual photoreceptor rhodopsin is providing the basis for the design of light-driven artificial molecular devices.

Conformational analysis: crystallographic, molecular mechanics and quantum chemical studies of C—H...O hydrogen bonding in the flexible bis(nosylate) derivative of catechol

2004 ◽  
Vol 60 (5) ◽  
pp. 598-608 ◽  
Author(s):  
Orde Quentin Munro ◽  
Lynette Mariah
Keyword(s):  
Hydrogen Bonding ◽  
Hydrogen Bonds ◽  
Crystal Lattice ◽  
Molecular Mechanics ◽  
Quantum Chemical ◽  
Critical Role ◽  
Crystalline Solid ◽  
Molecular Architecture ◽  
X Ray ◽  
Hydrogen Bonded

The single-crystal X-ray diffraction analysis of 2-{[(4-nitrophenoxy)sulfonyl]oxy}phenyl 4-nitrophenyl sulfate (4) reveals that an interesting intermolecular or extended structure (a one-dimensional hydrogen-bonded polymer) is formed because of pairs of intermolecular (aryl)C—H...O(nitro) hydrogen bonds between the C 2 symmetry monomer units. The axis of the hydrogen-bonded polymer runs co-linear with the [101] face diagonal of the monoclinic unit cell. Molecular mechanics calculations using a modified version of the MM+ force field and a random conformational search algorithm have been used to locate the important low-energy in vacuo conformations of (4). The MM-calculated conformation of (4) that most closely matches the X-ray structure lies some 26.5 kJ mol−1 higher in energy than the global minimum-energy conformation, consistent with the notion that the crystallographically observed molecular architecture of (4) is a local energy minimum in the absence of its crystal lattice environment. Since the X-ray conformation of (4) was correctly calculated only when all of the neighbouring molecules in the crystal lattice were included in the simulation, hydrogen bonding and other non-bonded interactions in the crystal lattice clearly dictate the experimentally observed conformation of (4). Quantum chemical calculations (AM1 method) confirm the critical role played by the intermolecular (aryl)C—H...O(nitro) hydrogen bonds in controlling the crystallographically observed conformation of (4) and show that self-recognition in this system by hydrogen bonding is favoured on electrostatic grounds. Collectively, the molecular simulations suggest that because the lowest-energy molecular conformation of (4) does not permit the formation of an extended hydrogen-bonded `supramolecular' structure, it is not the preferred conformation in the crystalline solid state.

scholarly journals Ab initio quantum-chemical computations of the absorption cross sections of HgX2 and HgXY (X, Y = Cl, Br, and I): molecules of interest in the Earth's atmosphere

2019 ◽  
Vol 21 (1) ◽  
pp. 455-467 ◽  
Author(s):  
Sebastian P. Sitkiewicz ◽  
Daniel Rivero ◽  
Josep M. Oliva-Enrich ◽  
Alfonso Saiz-Lopez ◽  
Daniel Roca-Sanjuán
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Cross Sections ◽  
Quantum Chemical ◽  
Electronic States ◽  
Absorption Cross ◽  
Spectrum Range ◽  
Mercury Halides ◽  
Quantum Chemical Computations ◽  
Structure Properties

The electronic-structure properties of the low-lying electronic states and the absorption cross sections of mercury halides have been determined within the UV-vis spectrum range (170 nm ≤ λphoton ≤ 600 nm).

Sign in / Sign up

Export Citation Format

Share Document