Computing vibrational properties in hydrogen‐bonded systems using quantum wavepacket ab initio molecular dynamics

Iyengar, Srinivasan S.

doi:10.1002/qua.22417

Cited by 11 publications

(21 citation statements)

References 120 publications

(209 reference statements)

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“…The ab intio molecular dynamics (AIMD) simulations involve performing quantum chemical calculations “on-the-fly” to obtain the potential energy and nuclear forces. − The simulations conducted here are similar to those discussed in refs , − ,, and . The atom-centered density matrix propagation (ADMP), ,,,,− AIMD technique, as implemented within the Gaussian series of electronic structure codes, has been employed in these studies. This method is briefly reviewed in Appendix A.…”

Section: Theoretical Methodsmentioning

confidence: 99%

Influence of Water on Anharmonicity, Stability, and Vibrational Energy Distribution of Hydrogen-Bonded Adducts in Atmospheric Reactions: Case Study of the OH + Isoprene Reaction Intermediate Using Ab Initio Molecular Dynamics

et al. 2011

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The effect of water on the stability and vibrational states of a hydroxy-isoprene adduct is probed through the introduction of 1-15 water molecules. It is found that when a static nuclear harmonic approximation is invoked there is a substantial red-shift of the alcohol O-H stretch (of the order of 800 cm(-1)) as a result of introduction of water. When potential energy surface sampling and associated anharmonicities are introduced through finite temperature ab initio dynamics, this hydroxy-isoprene OH stretch strongly couples with all the water vibrational modes as well as the hydroxy-isoprene OH bend modes. A new computational technique is introduced to probe the coupling between these modes. The method involves a two-dimensional, time-frequency analysis of the finite temperature vibrational properties. Such an analysis not only provides information about the modes that are coupled as a result of finite-temperature analysis, but also the temporal evolution of such coupling.

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Section: Theoretical Methodsmentioning

confidence: 99%

Influence of Water on Anharmonicity, Stability, and Vibrational Energy Distribution of Hydrogen-Bonded Adducts in Atmospheric Reactions: Case Study of the OH + Isoprene Reaction Intermediate Using Ab Initio Molecular Dynamics

et al. 2011

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“…In a series of recent publications, [1][2][3][4][5][6][7][8][9] we have introduced a methodology that accurately computes quantum dynamical effects in a subsystem while simultaneously treating the motion of the surrounding atoms and changes in electronic structure. The approach is quantum-classical [10][11][12][13][14][15][16][17] and involves the synergy between a time-dependent quantum wavepacket description and ab initio molecular dynamics.…”

Section: Introductionmentioning

confidence: 99%

Quantum wavepacket ab initio molecular dynamics: Generalizations using an extended Lagrangian treatment of diabatic states coupled through multireference electronic structure

Iyengar

2010

The Journal of Chemical Physics

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We present a generalization to our previously developed quantum wavepacket ab initio molecular dynamics ͑QWAIMD͒ method by using multiple diabatic electronic reduced single particle density matrices, propagated within an extended Lagrangian paradigm. The Slater determinantal wavefunctions associated with the density matrices utilized may be orthogonal or nonorthogonal with respect to each other. This generalization directly results from an analysis of the variance in electronic structure with quantum nuclear degrees of freedom. The diabatic electronic states are treated here as classical parametric variables and propagated simultaneously along with the quantum wavepacket and classical nuclei. Each electronic density matrix is constrained to be N-representable. Consequently two sets of new methods are derived: extended Lagrangian-QWAIMD ͑xLag-QWAIMD͒ and diabatic extended Lagrangian-QWAIMD ͑DxLag-QWAIMD͒. In both cases, the instantaneous potential energy surface for the quantum nuclear degrees of freedom is constructed from the diabatic states using an on-the-fly nonorthogonal multireference formalism. By introducing generalized grid-based electronic basis functions, we eliminate the basis set dependence on the quantum nucleus. Subsequent reuse of the two-electron integrals during the on-the-fly potential energy surface computation stage yields a substantial reduction in computational costs. Specifically, both xLag-QWAIMD and DxLag-QWAIMD turn out to be about two orders of magnitude faster than our previously developed time-dependent deterministic sampling implementation of QWAIMD. Energy conservation properties, accuracy of the associated potential surfaces, and vibrational properties are analyzed for a family of hydrogen bonded systems.

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“…As a model to represent the THz spectrum at 300 K, we have calculated the THz vibrations at the optimized geometry in the fixed cell for room-temperature (295 K) crystallographic data (blue bars in Figure ). First-principles molecular dynamics studies would be much better in some cases, − and we will perform them as future work. The fixed-cell calculation (blue bars) yields lower frequencies for all peaks 1–9 than the other two cases (red and black bars).…”

Section: Resultsmentioning

confidence: 99%

Temperature Dependence in the Terahertz Spectrum of Nicotinamide: Anharmonicity and Hydrogen-Bonded Network

et al. 2017

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We have investigated the terahertz-spectral property of nicotinamide focusing on the temperature dependence in the range of 14-300 K. We observed that almost all peaks in the terahertz spectrum of the nicotinamide crystal showed a remarkable shift with temperature, whereas the lowest-frequency peak at 34.8 cm showed a negligible shift with temperature. By analyzing the terahertz spectrum with the dispersion-corrected density functional theory calculations, we found that the difference in the temperature dependence of the peak shift is well understood in terms of the presence/absence of stretching vibration of the intermolecular hydrogen bond in the mode and the change of cell parameters. The anharmonicity in the dissociation potential energy of very weak intermolecular hydrogen bonding causes the remarkable peak shift with temperature in the terahertz spectrum of nicotinamide. This finding suggests that the assignment and identification of peaks in the terahertz spectrum are systematically enabled by temperature-dependent measurements.

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Computing vibrational properties in hydrogen‐bonded systems using quantum wavepacket ab initio molecular dynamics

Cited by 11 publications

References 120 publications

Influence of Water on Anharmonicity, Stability, and Vibrational Energy Distribution of Hydrogen-Bonded Adducts in Atmospheric Reactions: Case Study of the OH + Isoprene Reaction Intermediate Using Ab Initio Molecular Dynamics

Influence of Water on Anharmonicity, Stability, and Vibrational Energy Distribution of Hydrogen-Bonded Adducts in Atmospheric Reactions: Case Study of the OH + Isoprene Reaction Intermediate Using Ab Initio Molecular Dynamics

Quantum wavepacket ab initio molecular dynamics: Generalizations using an extended Lagrangian treatment of diabatic states coupled through multireference electronic structure

Temperature Dependence in the Terahertz Spectrum of Nicotinamide: Anharmonicity and Hydrogen-Bonded Network

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