Atomistic Modeling of Vibrational Action Spectra in Polyatomic Molecules: Nuclear Quantum Effects

2014 ◽  
Vol 118 (29) ◽  
pp. 5427-5436 ◽  
Author(s):  
F. Calvo ◽  
C. Falvo ◽  
P. Parneix
Keyword(s):  
Quantum Effects ◽  
Polyatomic Molecules ◽  
Atomistic Modeling ◽  
Action Spectra ◽  
Vibrational Action ◽  
Nuclear Quantum Effects

scholarly journals Sensitivity of Intra- and Intermolecular Interactions of Benzo[h]quinoline from Car–Parrinello Molecular Dynamics and Electronic Structure Inspection

2021 ◽  
Vol 22 (10) ◽  
pp. 5220
Author(s):  
Jarosław J. Panek ◽  
Joanna Zasada ◽  
Bartłomiej M. Szyja ◽  
Beata Kizior ◽  
Aneta Jezierska
Keyword(s):  
Molecular Dynamics ◽  
Electronic Structure ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Quantum Effects ◽  
Potential Of Mean Force ◽  
Probability Density Distribution ◽  
Donor And Acceptor ◽  
Nuclear Quantum Effects ◽  
Vibrational Features

The O-H...N and O-H...O hydrogen bonds were investigated in 10-hydroxybenzo[h]quinoline (HBQ) and benzo[h]quinoline-2-methylresorcinol complex in vacuo, solvent and crystalline phases. The chosen systems contain analogous donor and acceptor moieties but differently coupled (intra- versus intermolecularly). Car–Parrinello molecular dynamics (CPMD) was employed to shed light onto principle components of interactions responsible for the self-assembly. It was applied to study the dynamics of the hydrogen bonds and vibrational features as well as to provide initial geometries for incorporation of quantum effects and electronic structure studies. The vibrational features were revealed using Fourier transformation of the autocorrelation function of atomic velocity and by inclusion of nuclear quantum effects on the O-H stretching solving vibrational Schrödinger equation a posteriori. The potential of mean force (Pmf) was computed for the whole trajectory to derive the probability density distribution and for the O-H stretching mode from the proton vibrational eigenfunctions and eigenvalues incorporating statistical sampling and nuclear quantum effects. The electronic structure changes of the benzo[h]quinoline-2-methylresorcinol dimer and trimers were studied based on Constrained Density Functional Theory (CDFT) whereas the Electron Localization Function (ELF) method was applied for all systems. It was found that the bridged proton is localized on the donor side in both investigated systems in vacuo. The crystalline phase simulations indicated bridged proton-sharing and transfer events in HBQ. These effects are even more pronounced when nuclear quantization is taken into account, and the quantized Pmf allows the proton to sample the acceptor area more efficiently. The CDFT indicated the charge depletion at the bridged proton for the analyzed dimer and trimers in solvent. The ELF analysis showed the presence of the isolated proton (a signature of the strongest hydrogen bonds) only in some parts of the HBQ crystal simulation. The collected data underline the importance of the intramolecular coupling between the donor and acceptor moieties.

scholarly journals Dynamical strengthening of covalent and non-covalent molecular interactions by nuclear quantum effects at finite temperature

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
Huziel E. Sauceda ◽  
Valentin Vassilev-Galindo ◽  
Stefan Chmiela ◽  
Klaus-Robert Müller ◽  
Alexandre Tkatchenko
Keyword(s):  
Finite Temperature ◽  
Electrostatic Interactions ◽  
Zero Point ◽  
Quantum Effects ◽  
Van Der Waals Interactions ◽  
Interatomic Distances ◽  
Point Energy ◽  
Molecular Bond ◽  
Energy Surfaces ◽  
Nuclear Quantum Effects

AbstractNuclear quantum effects (NQE) tend to generate delocalized molecular dynamics due to the inclusion of the zero point energy and its coupling with the anharmonicities in interatomic interactions. Here, we present evidence that NQE often enhance electronic interactions and, in turn, can result in dynamical molecular stabilization at finite temperature. The underlying physical mechanism promoted by NQE depends on the particular interaction under consideration. First, the effective reduction of interatomic distances between functional groups within a molecule can enhance the n → π* interaction by increasing the overlap between molecular orbitals or by strengthening electrostatic interactions between neighboring charge densities. Second, NQE can localize methyl rotors by temporarily changing molecular bond orders and leading to the emergence of localized transient rotor states. Third, for noncovalent van der Waals interactions the strengthening comes from the increase of the polarizability given the expanded average interatomic distances induced by NQE. The implications of these boosted interactions include counterintuitive hydroxyl–hydroxyl bonding, hindered methyl rotor dynamics, and molecular stiffening which generates smoother free-energy surfaces. Our findings yield new insights into the versatile role of nuclear quantum fluctuations in molecules and materials.

scholarly journals Temperature-Independent Nuclear Quantum Effects on the Structure of Water

2017 ◽  
Vol 119 (7) ◽  
Author(s):  
Kyung Hwan Kim ◽  
Harshad Pathak ◽  
Alexander Späh ◽  
Fivos Perakis ◽  
Daniel Mariedahl ◽  
...  
Keyword(s):  
Quantum Effects ◽  
Structure Of Water ◽  
Nuclear Quantum Effects

scholarly journals On-the-Fly Ring-Polymer Molecular Dynamics Calculations of the Dissociative Photodetachment Process of the Oxalate Anion

Molecules ◽  
2021 ◽  
Vol 26 (23) ◽  
pp. 7250
Author(s):  
Yukinobu Takahashi ◽  
Yu Hashimoto ◽  
Kohei Saito ◽  
Toshiyuki Takayanagi
Keyword(s):  
Molecular Dynamics ◽  
Potential Energy ◽  
Quantum Effects ◽  
Experimental Spectrum ◽  
Computational Time ◽  
Oxalate Anion ◽  
Dissociative Photodetachment ◽  
Ring Polymer ◽  
Ring Polymer Molecular Dynamics ◽  
Nuclear Quantum Effects

The dissociative photodetachment dynamics of the oxalate anion, C2O4H− + hν → CO2 + HOCO + e−, were theoretically studied using the on-the-fly path-integral and ring-polymer molecular dynamics methods, which can account for nuclear quantum effects at the density-functional theory level in order to compare with the recent experimental study using photoelectron–photofragment coincidence spectroscopy. To reduce computational time, the force acting on each bead of ring-polymer was approximately calculated from the first and second derivatives of the potential energy at the centroid position of the nuclei beads. We find that the calculated photoelectron spectrum qualitatively reproduces the experimental spectrum and that nuclear quantum effects are playing a role in determining spectral widths. The calculated coincidence spectrum is found to reasonably reproduce the experimental spectrum, indicating that a relatively large energy is partitioned into the relative kinetic energy between the CO2 and HOCO fragments. This is because photodetachment of the parent anion leads to Franck–Condon transition to the repulsive region of the neutral potential energy surface. We also find that the dissociation dynamics are slightly different between the two isomers of the C2O4H− anion with closed- and open-form structures.

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