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.

Stereodynamics of chemical reactions: quasi-classical, quantum and mixed quantum-classical theories

Open Physics ◽  
2012 ◽  
Vol 10 (2) ◽  
Author(s):  
Wenwu Xu ◽  
Guangjiu Zhao
Keyword(s):  
Chemical Reactions ◽  
Classical Method ◽  
Zero Point ◽  
Quantum Effects ◽  
Classical Trajectory ◽  
Tunneling Effect ◽  
Point Energy ◽  
Classical Quantum ◽  
Theoretical Results ◽  
Good Agreement

AbstractIn this review, some benchmark works by Han and coworkers on the stereodynamics of typical chemical reactions, triatomic reactions H + D2, Cl + H2 and O + H2 and polyatomic reaction Cl+CH4/CD4, are presented by using the quasi-classical, quantum and mixed quantum-classical methods. The product alignment and orientation in these A+BC model reactions are discussed in detail. We have also compared our theoretical results with experimental measurements and demonstrated that our theoretical results are in good agreement with the experimental results. Quasi-classical trajectory (QCT) method ignores some quantum effects like the tunneling effect and zero-point energy. The quantum method will be very time-consuming. Moreover, the mixed quantum-classical method can take into account some quantum effects and hence is expected to be applicable to large systems and widely used in chemical stereodynamics studies.

FINITE TEMPERATURE RESULTS FROM CONSTRAINED FERMIONIZATION IN THE 2-D SPIN 1/2 HEISENBERG ANTIFERROMAGNET II: FLUCTUATIONS IN THE DIMER PHASES

1994 ◽  
Vol 08 (06) ◽  
pp. 757-776 ◽  
Author(s):  
M. DI STASIO ◽  
A. TAGLIACOZZO ◽  
E. ERCOLESSI ◽  
G. MORANDI
Keyword(s):  
Saddle Point ◽  
Specific Heat ◽  
Finite Temperature ◽  
Site Occupancy ◽  
Zero Point ◽  
Single Site ◽  
Heisenberg Antiferromagnet ◽  
Zero Point Energy ◽  
Saddle Point Approximation ◽  
Point Energy

The constraint of single-site occupancy is implemented in the fermionization of the model, within the saddle point approximation. The columnar and the staggered dimer phases are studied and the contribution of the fluctuations to the zero point energy and the specific heat is analyzed.

scholarly journals Significance of nuclear quantum effects in hydrogen bonded molecular chains

2021 ◽  
Author(s):  
Ales Cahlik ◽  
Jack Hellerstedt ◽  
Jesus Mendieta-Moreno ◽  
Martin Švec ◽  
Vijai Santhini ◽  
...  
Keyword(s):  
Proton Transfer ◽  
Mechanical Stability ◽  
Dominant Role ◽  
Zero Point ◽  
Quantum Effects ◽  
Molecular Networks ◽  
Hydrogen Bonded Systems ◽  
Low Dimensional ◽  
Nuclear Quantum Effects ◽  
Hydrogen Bonded

Abstract In hydrogen bonded systems, nuclear quantum effects such as zero-point motion and tunneling can significantly affect their material properties through underlying physical and chemical processes. Presently, direct observation of the influence of nuclear quantum effects on the strength of hydrogen bonds with resulting structural and electronic implications remains elusive, leaving opportunities for deeper understanding to harness their fascinating properties. We studied hydrogen-bonded one-dimensional quinonediimine molecular networks which may adopt two isomeric electronic configurations via proton transfer. Herein, we demonstrate that concerted proton transfer promotes a delocalization of π-electrons along the molecular chain, which enhances the cohesive energy between molecular units, increasing the mechanical stability of the chain and giving rise to new electronic in-gap states localized at the ends. These findings demonstrate the identification of a new class of isomeric hydrogen bonded molecular systems where nuclear quantum effects play a dominant role in establishing their chemical and physical properties. We anticipate that this work will open new research directions towards the control of mechanical and electronic properties of low-dimensional molecular materials via concerted proton tunneling.

scholarly journals Decisive role of nuclear quantum effects on surface mediated water dissociation at finite temperature

2018 ◽  
Vol 148 (10) ◽  
pp. 102320 ◽  
Author(s):  
Yair Litman ◽  
Davide Donadio ◽  
Michele Ceriotti ◽  
Mariana Rossi
Keyword(s):  
Finite Temperature ◽  
Decisive Role ◽  
Quantum Effects ◽  
Water Dissociation ◽  
Nuclear Quantum Effects

scholarly journals Characterizing Quantum Effects in Optically Induced Nanowire Self-Oscillations: Coherent Properties

Photonics ◽  
2021 ◽  
Vol 8 (7) ◽  
pp. 237
Author(s):  
Jeong-Ryeol Choi
Keyword(s):  
Mechanical Properties ◽  
Driving Force ◽  
Zero Point ◽  
Quantum Effects ◽  
Time Behavior ◽  
Point Energy ◽  
Quantum Energy ◽  
Probability Densities ◽  
Intrinsic Oscillation ◽  
The Mean

Mechanical properties of metallic-nanowire self-oscillations are investigated through a coherent-state analysis. We focus on elucidating the time behavior of quantum energy in such oscillations, in addition to the analysis of fluctuations, evolution of eigenstates, and oscillatory trajectories. The quantum energy varies somewhat randomly at first, but, at a later time, it undergoes a stable periodical oscillation; the mean energy in the stabilized motion is large when the frequency of the driving force is resonated with that of the intrinsic oscillation of the nanowire. We confirmed that when the oscillatory amplitude is sufficiently low, the quantum energy is quite different from the classical one due to zero-point energy, which appears in the quantum regime. Because the power in such an oscillation is typically ultra low, quantum effects in the nanowire oscillations are non-negligible. Detailed analysis for the evolution of the probability densities and their relation with the oscillation trajectories of the nanowire are also carried out. Characterizing quantum effects in the actual oscillatory motions and clarifying their difference from the classical ones are important in understanding nanowire self-oscillations.

Charge distributions and chemical effects. XLV. Graphite

1988 ◽  
Vol 66 (10) ◽  
pp. 2631-2633 ◽  
Author(s):  
Andrea Peluso ◽  
Sándor Fliszár
Keyword(s):  
Heat Content ◽  
Zero Point ◽  
Van Der Waals Interactions ◽  
Bond Energies ◽  
Net Charge ◽  
Point Energy ◽  
Bond Forming ◽  
Experimental Heat ◽  
Chemical Effects ◽  
Debye Temperatures

The zero point energy of graphite, [Formula: see text], is deduced from Debye's theory by separating the lattice vibrations into two approximately independent parts, with Debye temperatures [Formula: see text] (in plane) and [Formula: see text] (perpendicular). A balanced evaluation gives [Formula: see text]. The bond energies of graphite in its potential minimum are derived from those of polynuclear benzenoїd hydrocarbons using a formula describing bond energies in terms of the charges at the bond-forming atoms. These energies plus a consideration of (i) van der Waals interactions between layers (~1.2 kcal mol−1), (ii) ZPE = 3.68, and (iii) the experimental heat content. HT − H0 = 0.25 kcal mol−1, lead to a theoretical enthalpy of atomization, ΔHa(298.15) = 174.6, which is ~2% larger than its experimental counterpart, 170.9 kcal mol−1. Exploiting the fact that the carbon atoms are electroneutral in graphite and not so in benzenoїd hydrocarbons, the results obtained for graphite support the approximate validity of bond energies deduced for polynuclear benzenoїd hydrocarbons and of the net charge, 14.8 × 10−3 e, deduced for the carbon atom of benzene.

scholarly journals Polyelectrolytes induce water-water correlations that result in dramatic viscosity changes and nuclear quantum effects

2019 ◽  
Vol 5 (12) ◽  
pp. eaay1443 ◽  
Author(s):  
J. Dedic ◽  
H. I. Okur ◽  
S. Roke
Keyword(s):  
Long Range ◽  
Electrostatic Interactions ◽  
Second Harmonic ◽  
Mean Field ◽  
Quantum Effects ◽  
Field Approximation ◽  
Mean Field Approximation ◽  
Hydration Shells ◽  
Polyelectrolyte Solutions ◽  
Nuclear Quantum Effects

Ions interact with water via short-ranged ion-dipole interactions. Recently, an additional unexpected long-ranged interaction was found: The total electric field of ions influences water-water correlations over tens of hydration shells, leading to the Jones Ray effect, a 0.3% surface tension depression. Here, we report such long-range interactions contributing substantially to both molecular and macroscopic properties. Femtosecond elastic second harmonic scattering (fs-ESHS) shows that long-range electrostatic interactions are remarkably strong in aqueous polyelectrolyte solutions, leading to an increase in water-water correlations. This increase plays a role in the reduced viscosity, which changes more than two orders of magnitude with polyelectrolyte concentration. Using D2O instead of H2O shifts both the fs-ESHS and the viscosity curve by a factor of ~10 and reduces the maximum viscosity value by 20 to 300%, depending on the polyelectrolyte. These phenomena cannot be explained using a mean-field approximation of the solvent and point to nuclear quantum effects.

scholarly journals Does glycosyl transfer involve an oxacarbenium intermediate? Computational simulation of the lifetime of the methoxymethyl cation in water

2011 ◽  
Vol 83 (8) ◽  
pp. 1507-1514 ◽  
Author(s):  
Ian H. Williams ◽  
J. Javier Ruiz Pernía ◽  
Iñaki Tuñón
Keyword(s):  
Free Energy ◽  
Computational Simulation ◽  
Zero Point ◽  
Md Simulations ◽  
Quantum Corrections ◽  
Water Molecules ◽  
Point Energy ◽  
Classical Estimate ◽  
High Level ◽  
Energy Surfaces

2D free-energy surfaces for transfer of the methoxymethyl cation between two water molecules are constructed from molecular dynamics (MD) simulations in which these atoms are treated quantum-mechanically within a box of 1030 classical solvent water molecules at 300 K. This provides a simple model for glycosyl transfer in water. The AM1/TIP3P surfaces with 2D-spline corrections at either MPWB1K/6-31+G(d,p) or MP2/6-31+G(d,p) contain a shallow free-energy well corresponding to an oxacarbenium ion intermediate in a DN*AN mechanism. MD analysis at three temperatures leads to a classical estimate of the lifetime of the methoxymethyl cation in water; when quantum corrections for vibrational zero-point energy are included, the lifetime is estimated to be about 1 ps, in agreement with the best experimental estimate. This suggests that computational simulation, with appropriate high-level correction, is a reliable tool to obtain detailed and reliable mechanistic descriptions for glycosidases. In view of the importance of developing improved anti-influenza drugs, simulations of sialidases that considered both sialyl oxacarbenium ion and covalent sialyl-enzyme as possible intermediates could provide particular insight.

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