Polarizabilities of hydrogen molecules calculated without using the Born-Oppenheimer approximation

The stability of four fermionic particles with unit charge, of which two are positively and two negatively charged, is discussed. Except for using the simplest approximation of a single Gaussian orbital per particle, the problem is exactly solved variationally by varying the masses to simulate molecular di-hydrogen, mono-muonated di-hydrogen, and di-muonated di-hydrogen. We illustrate the celebrated Born–Oppenheimer approximation 2 years after the occasion of its 90th anniversary. It is suggested that this method is valid only for di-hydrogen.

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Effects of Cooking Processes on Breath Hydrogen and Colonic Fermentation of Soybean

Current Nutrition & Food Science ◽

10.2174/1573401316666200226104601 ◽

2020 ◽

Vol 16 (4) ◽

pp. 488-493

Author(s):

Naoya Okumura ◽

Naoya Jinno ◽

Kentaro Taniguchi ◽

Kenichi Tanabe ◽

Sadako Nakamura ◽

...

Keyword(s):

Healthy Adult ◽

Area Under The Curve ◽

Cooking Methods ◽

Breath Hydrogen ◽

Gas Chromatograph ◽

Colonic Fermentation ◽

Hydrogen Molecules ◽

Nutritional Analysis ◽

Hydrogen Level ◽

Adult Volunteers

Background: Soybean is rich in dietary fibers; consequently, soybean ingestion considerably increases the breath level of hydrogen molecules via anaerobic colonic fermentation. However, the influence of cooking methods on this effect, which can affect the overall health benefits of soybean, remains unknown. Objectives: The aim is to examine whether different methods of cooking soybean affect the colonic fermentation process. Methods: Nine healthy adult volunteers participated in the study; they ingested either roasted soybean flour (kinako) or well-boiled soybean (BS). Differences in their breath components were compared. Both test meals were cooked using 80 g of soybeans per individual. After a 12 h fast, the participants ate the test meals, and their breath hydrogen level was analyzed every 1 h for 9 h by using a gas chromatograph with a semiconductor detector. In addition, particle size distribution and soluble/ insoluble fibers in the feces were examined. Results: The oro-cecal transit time did not significantly differ between individuals who ingested kinako and BS. However, the area under the curve between 7 and 9 h after the ingestion of BS was significantly increased compared with that after the ingestion of kinako. The nutritional analysis indicated that the content of both soluble and insoluble fibers in BS was higher than that in kinako. In addition, the levels of unfermented fragments and soluble/insoluble fibers in the feces were increased after the ingestion of kinako compared with those after the ingestion of kinako. Conclusion: Cooking methods alter the composition of non-digestible fibers in soybean, and this can result in the lack of fermentative particles in the feces, thereby causing alterations in the breath level of hydrogen via colonic fermentation.

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Coupled-pair theories and Davidson-type corrections for quasidegenerate states: The H4 model revisited

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19881919 ◽

1988 ◽

Vol 53 (9) ◽

pp. 1919-1942 ◽

Cited By ~ 71

Author(s):

Josef Paldus ◽

Paul E. S. Wormer ◽

Marc Benard

Keyword(s):

Electron Correlation ◽

Model System ◽

Coupled Cluster ◽

Electron Model ◽

Hydrogen Molecules ◽

Double Zeta ◽

Correlation Problem ◽

Variational Approaches ◽

Cluster Type ◽

The Many

The performance of various variational and non-variational approaches to the many-electron correlation problem is examined for a simple four-electron model system consisting of two stretched hydrogen molecules in trapezoidal, rectangular and linear configurations, in which the degree of quasi-degeneracy can be continuously varied from a non-degenerate to an almost degenerate situation. In contrast to an earlier work (K. Jankowski and J. Paldus, Int. J. Quantum Chem. 18, 1243 (1980)) we employ a double-zeta plus polarization basis and examine both single reference and multireference configuration interaction and coupled-cluster-type approaches. The performance of various Davidson-type corrections is also investigated.

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Introduction

10.1093/oso/9780198805014.003.0001 ◽

2018 ◽

Author(s):

Niels Engholm Henriksen ◽

Flemming Yssing Hansen

Keyword(s):

Schrödinger Equation ◽

Schrodinger Equation ◽

Degrees Of Freedom ◽

State Level ◽

Boltzmann Distribution ◽

Theoretical Description ◽

Time Dependent ◽

Nuclear Dynamics ◽

Molecular Reaction ◽

Oppenheimer Approximation

This introductory chapter considers first the relation between molecular reaction dynamics and the major branches of physical chemistry. The concept of elementary chemical reactions at the quantized state-to-state level is discussed. The theoretical description of these reactions based on the time-dependent Schrödinger equation and the Born–Oppenheimer approximation is introduced and the resulting time-dependent Schrödinger equation describing the nuclear dynamics is discussed. The chapter concludes with a brief discussion of matter at thermal equilibrium, focusing at the Boltzmann distribution. Thus, the Boltzmann distribution for vibrational, rotational, and translational degrees of freedom is discussed and illustrated.

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Influence of Kubas-type interaction of B–Ni codoped graphdiyne with hydrogen molecules on desorption temperature and storage efficiency

Materials Today Energy ◽

10.1016/j.mtener.2020.100421 ◽

2020 ◽

Vol 16 ◽

pp. 100421

Author(s):

E.V. Anikina ◽

A. Banerjee ◽

V.P. Beskachko ◽

R. Ahuja

Keyword(s):

Storage Efficiency ◽

Desorption Temperature ◽

Hydrogen Molecules ◽

Type Interaction ◽

And Storage

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Full-dimensional quantum stereodynamics of the non-adiabatic quenching of OH(A2Σ+) by H2

Nature Chemistry ◽

10.1038/s41557-021-00730-1 ◽

2021 ◽

Author(s):

Bin Zhao ◽

Shanyu Han ◽

Christopher L. Malbon ◽

Uwe Manthe ◽

David. R. Yarkony ◽

...

Keyword(s):

Quantum Dynamics ◽

Previous Analysis ◽

Branching Ratio ◽

Energy Matrix ◽

Elastic Channel ◽

Electronically Excited ◽

Oppenheimer Approximation ◽

Electronic Motion ◽

Adiabatic Dynamics ◽

Good Agreement

AbstractThe Born–Oppenheimer approximation, assuming separable nuclear and electronic motion, is widely adopted for characterizing chemical reactions in a single electronic state. However, the breakdown of the Born–Oppenheimer approximation is omnipresent in chemistry, and a detailed understanding of the non-adiabatic dynamics is still incomplete. Here we investigate the non-adiabatic quenching of electronically excited OH(A2Σ+) molecules by H2 molecules using full-dimensional quantum dynamics calculations for zero total nuclear angular momentum using a high-quality diabatic-potential-energy matrix. Good agreement with experimental observations is found for the OH(X2Π) ro-vibrational distribution, and the non-adiabatic dynamics are shown to be controlled by stereodynamics, namely the relative orientation of the two reactants. The uncovering of a major (in)elastic channel, neglected in a previous analysis but confirmed by a recent experiment, resolves a long-standing experiment–theory disagreement concerning the branching ratio of the two electronic quenching channels.

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High-Fidelity First Principles Nonadiabaticity: Diabatization, Analytic Representation of Global Diabatic Potential Energy Matrices, and Quantum Dynamics

Physical Chemistry Chemical Physics ◽

10.1039/d1cp03008f ◽

2021 ◽

Author(s):

Yafu Guan ◽

Changjian Xie ◽

David R. Yarkony ◽

Hua Guo

Keyword(s):

Potential Energy ◽

Excited States ◽

First Principles ◽

Quantum Dynamics ◽

Chemical Processes ◽

High Fidelity ◽

Nonadiabatic Dynamics ◽

Electronically Excited States ◽

Electronically Excited ◽

Oppenheimer Approximation

Nonadiabatic dynamics, which goes beyond the Born-Oppenheimer approximation, has increasingly been shown to play an important role in chemical processes, particularly those involving electronically excited states. Understanding multistate dynamics requires...

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An Investigation into the Approximations Used in Wave Packet Molecular Dynamics for the Study of Warm Dense Matter

Plasma ◽

10.3390/plasma4020020 ◽

2021 ◽

Vol 4 (2) ◽

pp. 294-308

Author(s):

William A. Angermeier ◽

Thomas G. White

Keyword(s):

Molecular Dynamics ◽

Wave Packet ◽

Hydrogen Plasma ◽

Valence Bond ◽

Dense Matter ◽

Basis Set ◽

Warm Dense Matter ◽

Scaling Parameters ◽

Oppenheimer Approximation ◽

Semi Empirical

Wave packet molecular dynamics (WPMD) has recently received a lot of attention as a computationally fast tool with which to study dynamical processes in warm dense matter beyond the Born–Oppenheimer approximation. These techniques, typically, employ many approximations to achieve computational efficiency while implementing semi-empirical scaling parameters to retain accuracy. We investigated three of the main approximations ubiquitous to WPMD: a restricted basis set, approximations to exchange, and the lack of correlation. We examined each of these approximations in regard to atomic and molecular hydrogen in addition to a dense hydrogen plasma. We found that the biggest improvement to WPMD comes from combining a two-Gaussian basis with a semi-empirical correction based on the valence-bond wave function. A single parameter scales this correction to match experimental pressures of dense hydrogen. Ultimately, we found that semi-empirical scaling parameters are necessary to correct for the main approximations in WPMD. However, reducing the scaling parameters for more ab-initio terms gives more accurate results and displays the underlying physics more readily.

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