scholarly journals Classification of hydrogen bond flips in small water polyhedra applied to concerted proton tunneling

2016 ◽  
Vol 18 (39) ◽  
pp. 27351-27357 ◽  
Author(s):  
M. V. Kirov

Graph theoretical representation of the tunneling states of a water hexamer.

1996 ◽  
Vol 226 (1-3) ◽  
pp. 157-160 ◽  
Author(s):  
Sadamu Takeda ◽  
Fumitaka Kondoh ◽  
Nobuo Nakamura ◽  
Kizashi Yamaguchi

2020 ◽  
Vol 120 (19) ◽  
Author(s):  
Shuman Li ◽  
Alireza Azizi ◽  
Steven R. Kirk ◽  
Samantha Jenkins

2000 ◽  
Vol 44 (1) ◽  
pp. 227-228 ◽  
Author(s):  
A. Takasu ◽  
K. Watanabe ◽  
G. Kawai

Author(s):  
Zi Li ◽  
Yong Yang ◽  
Xing Nie ◽  
Tianlv Xu ◽  
Steven Kirk ◽  
...  

We seek to determine the two-way transfer of chemical character due to the coupling occurring between hydrogen-bonds and covalent-bonds known to account for the unusual strength of hydrogen-bonds in water. We have provided a vector-based quantification of the chemical character of uncoupled hydrogen-bonds and covalent-bonds and then determined the effects of two-way coupling consistent with the total local energy density H(rb) < 0 for hydrogen-bonds. We have calculated the precessions Kʹ of the eigenvectors around the bond-path for the Ehrenfest Force F(r) and compared with the corresponding QTAIM Kʹ. In doing so we explain why the Ehrenfest Force F(r) provides insights into the coupling between the hydrogen and covalent bonds whilst QTAIM cannot. Conditions for favorable transfer of electron momentum from the hydrogen atom of a sigma bond to the hydrogen-bond are found, with excellent agreement with the hydrogen-bond BCP and covalent-bond BCP separations providing the theoretical bounds for coupling.


2012 ◽  
Vol 10 (4) ◽  
pp. 1318-1327
Author(s):  
Yaroslava Pushkarova ◽  
Yuriy Kholin

AbstractThe Taft-Kamlet-Abboud hydrogen-bond acidity, hydrogen-bond basicity and polarity-polarizability are widely used as empirical characteristics of solvent-solute interactions. These solvatochromic parameters are determined from the absorption band positions of solvatochromic probes in the standard medium and in the medium under study. The practice of solvatochromic probing is growing rapidly, and the values of solvatochromic parameters are refined from time to time. As these values are rather close for many media, the classification of media based on these values can be tedious. This increases the choice of algorithms that can be employed in order to decrease the ambiguity of classification. The classification algorithms stable to small variations of solvatochromic parameters are of special interest. The artificial neural networks (ANN) proved to be a powerful tool for the supervised classification. The paper focuses on the search of optimal parameters of probabilistic, dynamic, Elman, feed-forward, and cascade ANN for the classification of solvent on the basis of their solvatochromic characteristics. Also, the influence of data variation on the stability of classification is examined. The dynamic and probabilistic neural networks have been found to be error-free and stable; they have significantly become such a common tool for supervised classification as linear discriminant analysis.


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