CNDO/2 Study of C2H2 + H2O System

Different configurations of the C2H2 + H2O system obtained by various translations and rotations of H2O around the C2H2 molecule were studied. The two molecules were found to form not only hydrogen bond but also a charge transfer complex

Information Theory in Describing the Electronic Structures of Atoms

An information approach to the description of atoms by introducing »differential« entropy characteristics of chemical elements has been developed. These quantities clearly reflect the horizontal and vertical structure of the periodic table, and the main features of atomic electron structures, such as delay in filling d- and f-subshells, the action of Hund\u27s first rule, the anomalies in the electronic structure of some atoms, the appearance of the first electron having a given value of some quantum number, etc. The necessity of change in the position of lanthanides and actinides in the periodic table is discussed

Information inequalities and Generalized Graph Entropies

In this article, we discuss the problem of establishing relations between information measures assessed for network structures. Two types of entropy based measures namely, the Shannon entropy and its generalization, the R\'{e}nyi entropy have been considered for this study. Our main results involve establishing formal relationship, in the form of implicit inequalities, between these two kinds of measures when defined for graphs. Further, we also state and prove inequalities connecting the classical partition-based graph entropies and the functional-based entropy measures. In addition, several explicit inequalities are derived for special classes of graphs.Comment: A preliminary version. To be submitted to a journa

Representations and descriptors unifying the study of molecular and bulk systems

Establishing a unified framework for describing the structures of molecular and periodic systems is a long-standing challenge in physics, chemistry, and material science. With the rise of machine learning methods in these fields, there is a growing need for such a method. This perspective aims to discuss the development and use of three promising approaches-topological, atom-density, and symmetry-based-for the prediction and rationalization of physical, chemical, and mechanical properties of atomistic systems across different scales and compositions

Connections between Classical and Parametric Network Entropies

This paper explores relationships between classical and parametric measures of graph (or network) complexity. Classical measures are based on vertex decompositions induced by equivalence relations. Parametric measures, on the other hand, are constructed by using information functions to assign probabilities to the vertices. The inequalities established in this paper relating classical and parametric measures lay a foundation for systematic classification of entropy-based measures of graph complexity

A Theoretical Information Approach to Ring and Total Aromaticity in Ground and Excited States

Applying the Shannon equation to the density matrix of a molecule, an information index is specified for the quantitative estimation of the ring and total aromaticity of molecules in ground · and excited states. The approach is applicable within each LCAO- method. The information index reproduces well the classification of molecules as aromatic, nonaromatic, and antiaromatic. It also correlates with results of other authors obtained by radically different approaches. A tendency is found for the aromaticity of aromatic molecules to decrease and of antiaromatic molecules to increase when the molecule is excited to the S1-state

Information Indices with High Discriminative Power for Graphs

In this paper, we evaluate the uniqueness of several information-theoretic measures for graphs based on so-called information functionals and compare the results with other information indices and non-information-theoretic measures such as the well-known Balaban index. We show that, by employing an information functional based on degree-degree associations, the resulting information index outperforms the Balaban index tremendously. These results have been obtained by using nearly 12 million exhaustively generated, non-isomorphic and unweighted graphs. Also, we obtain deeper insights on these and other topological descriptors when exploring their uniqueness by using exhaustively generated sets of alkane trees representing connected and acyclic graphs in which the degree of a vertex is at most four

On Characterization of Monocyclic Structures

The sum of topological distances in the molecular graph, the Wiener number, is used for a topological characterization of monocycles. Various other mathematical models based either on the adjacency matrix or on the distance matrix of a system, which were earlier used mostly for studying molecular branching, are now also applied to monocyclic structures in order to learn if they would be of use in characterizing molecular cyclicity