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2 results on '"Qm/Mm/Pcm"'

1. Integrated computational approaches for spectroscopic studies of molecular systems in the gas phase and in solution: pyrimidine as a test case.

Author

Biczysko, Malgorzata, Bloino, Julien, Brancato, Giuseppe, Cacelli, Ivo, Cappelli, Chiara, Ferretti, Alessandro, Lami, Alessandro, Monti, Susanna, Pedone, Alfonso, Prampolini, Giacomo, Puzzarini, Cristina, Santoro, Fabrizio, Trani, Fabio, and Villani, Giovanni

Subjects
*PHASE transitions, *SOLUTION (Chemistry), *RELAXATION phenomena, *PYRIMIDINES, *QUANTUM theory, *MOLECULAR structure, *ULTRAVIOLET spectroscopy, *MOLECULAR dynamics, *HARTREE-Fock approximation
Abstract

An integrated computational approach built on quantum mechanical (QM) methods, purposely tailored inter- and intra-molecular force fields and continuum solvent models combined with time-independent and time-dependent schemes to account for nuclear motion effects is applied to the spectroscopic investigation of pyrimidine in the gas phase as well as in aqueous and CCl solutions. Accurate post-Hartree-Fock methodologies are employed to compute molecular structure, harmonic vibrational frequencies, energies and oscillator strengths for electronic transitions in order to validate the accuracy of approaches rooted into density functional theory with emphasis also on hybrid QM/QM′ models. Within the time-independent approaches, IR spectra are computed including anharmonicities through perturbative corrections while UV-vis line-shapes are simulated accounting for the vibrational structure; in both cases, the environmental effects are described by continuum models. The effects of conformational flexibility, including solvent dynamics, are described through time-dependent models based on purposely DFT-tailored force fields applied to molecular dynamics simulations and on QM computations of spectroscopic properties. Such procedures are exploited to simulate IR and UV-vis spectra of pyrimidine in the gas phase and in solutions, leading in all cases to good agreement with experimental observations and allowing to dissect different effects underlying spectral phenomena. [ABSTRACT FROM AUTHOR]

Published
2012
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2. Integrated computational approaches for spectroscopic studies of molecular systems in the gas phase and in solution: pyrimidine as a test case

Author

Chiara Cappelli, Fabrizio Santoro, Cristina Puzzarini, Malgorzata Biczysko, F. Trani, Ivo Cacelli, Giacomo Prampolini, Susanna Monti, Giovanni Villani, Alfonso Pedone, Alessandro Lami, Julien Bloino, Giuseppe Brancato, Alessandro Ferretti, M. Biczysko, J. Bloino, G. Brancato, I. Cacelli, C. Cappelli, A. Ferretti, A. Lami, S. Monti, A. Pedone, G. Prampolini, C. Puzzarini, F. Santoro, F. Trani, G. Villani, Biczysko, M., Bloino, J., Brancato, Giuseppe, Cacelli, I., Cappelli, Chiara, Ferretti, A., Lami, A., Monti, S., Pedone, A., Prampolini, G., Puzzarini, C., Santoro, F., Trani, F., and Villani, G.

Subjects
Resonance Raman, Anharmonic Vibrational Properties, Molecular dynamic, Computational spectroscopy, Composite schemes - Hybrid model, Solvation Models, Polarizable continuum model, Dft, Integrated approaches, Force-Fields, Molecular dynamics, Time-independent approaches, Harmonic Approximation, Solvent effects, Time-dependent approache, Vertical excitation energies, Chemistry, Ccsd(T), Anharmonicity, Vibrational spectra, Electronic Excitation-Energies, Hybrid models, Solvent models, Linear-Response Methods, Composite schemes, Density functional theory, Vertical excitation energies Electronic spectra Spectra line-shape Vibronic transitions UV–vi, Atomic physics, Post-Hartree–Fock, Resonance Raman - Vibrational spectra - IR intensities - Anharmonicity, Time-dependent approaches, Density-Functional Computations, UV-vis, Post-Hartree-Fock, Electronic spectra, Solvent effect, Qm/Mm/Pcm, Ab initio quantum chemistry methods, Force field, Physical and Theoretical Chemistry, Time-independent approache, Integrated approache, Force fields, Vibronic transitions, Polarizable Continuum Model, Ab-Initio Calculations, Multireference Perturbation Ci, Computational physics, QM/MM/PCM , DFT , Post-Hartree–Fock CCSD(T), Spectra line-shape, IR intensities
Abstract

An integrated computational approach built on quantum mechanical (QM) methods, purposely tailored inter- and intra-molecular force fields and continuum solvent models combined with time-independent and time- dependent schemes to account for nuclear motion effects is applied to the spectroscopic investigation of pyrimidine in the gas phase as well as in aqueous and CCl4 solutions. Accurate post-Hartree–Fock methodologies are employed to compute molecular structure, harmonic vibrational frequencies, energies and oscillator strengths for electronic transitions in order to validate the accuracy of approaches rooted into density functional theory with emphasis also on hybrid QM/QM0 models. Within the time-independent approaches, IR spectra are computed including anharmonicities through perturbative corrections while UV–vis line-shapes are simulated accounting for the vibrational structure; in both cases, the environmental effects are described by continuum models. The effects of conformational flexibility, including solvent dynamics, are described through time-dependent models based on purposely DFT-tailored force fields applied to molecular dynamics simulations and on QM computations of spectroscopic properties. Such procedures are exploited to simulate IR and UV–vis spectra of pyrimidine in the gas phase and in solutions, leading in all cases to good agreement with experimental observations and allowing to dissect different effects underlying spectral phenomena.

Published
2013
Full Text
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