scholarly journals Two theorems on connectivity indices

2002 ◽  
Vol 67 (2) ◽  
pp. 99-102 ◽  
Author(s):  
Ivan Gutman
Keyword(s):  
Connectivity Index ◽  
Connectivity Indices

Two general cases are pointed out for which the ordering of molecules according to the connectivity index C(?) is the same for all values of the exponent ?.

scholarly journals Ordering of alkane isomers by means of connectivity indices

2002 ◽  
Vol 67 (2) ◽  
pp. 87-97 ◽  
Author(s):  
Ivan Gutman ◽  
Dusica Vidovic ◽  
Anka Nedic
Keyword(s):  
Carbon Atom ◽  
Organic Molecule ◽  
Molecular Graph ◽  
Connectivity Index ◽  
Randić Index ◽  
Randic Index ◽  
Connectivity Indices ◽  
The Difference

The connectivity index of an organic molecule whose molecular graph is Gis defined as C(?)=?(?u?v)??where ?u is the degree of the vertex u in G, where the summation goes over all pairs of adjacent vertices of G and where ? is a pertinently chosen exponent. The usual value of ? is ?1/2, in which case ?=C(?1/2) is referred to as the Randic index. The ordering of isomeric alkanes according to ??follows the extent of branching of the carbon-atom skeleton. We now study the ordering of the constitutional isomers of alkanes with 6 through 10 carbon atoms with respect to C(?) for various values of the parameter ?. This ordering significantly depends on ?. The difference between the orderings with respect to ??and with respect to C(?) is measured by a function ??and the ?-dependence of ??was established.

scholarly journals Some Eccentricity-Based Topological Indices and Polynomials of Poly(EThyleneAmidoAmine) (PETAA) Dendrimers

Processes ◽  
2019 ◽  
Vol 7 (7) ◽  
pp. 433 ◽  
Author(s):  
Jialin Zheng ◽  
Zahid Iqbal ◽  
Asfand Fahad ◽  
Asim Zafar ◽  
Adnan Aslam ◽  
...  
Keyword(s):  
Molecular Descriptors ◽  
Molecular Graph ◽  
Topological Indices ◽  
Molecular Structures ◽  
Connectivity Index ◽  
Connectivity Indices ◽  
Numerical Invariants ◽  
Explicit Representations ◽  
Pharmaceutical Properties

Topological indices have been computed for various molecular structures over many years. These are numerical invariants associated with molecular structures and are helpful in featuring many properties. Among these molecular descriptors, the eccentricity connectivity index has a dynamic role due to its ability of estimating pharmaceutical properties. In this article, eccentric connectivity, total eccentricity connectivity, augmented eccentric connectivity, first Zagreb eccentricity, modified eccentric connectivity, second Zagreb eccentricity, and the edge version of eccentric connectivity indices, are computed for the molecular graph of a PolyEThyleneAmidoAmine (PETAA) dendrimer. Moreover, the explicit representations of the polynomials associated with some of these indices are also computed.

scholarly journals On molecular topological properties of diamond-like networks

2017 ◽  
Vol 95 (7) ◽  
pp. 758-770 ◽  
Author(s):  
Muhammad Imran ◽  
Abdul Qudair Baig ◽  
Hafiz Muhammad Afzal Siddiqui ◽  
Rabia Sarwar
Keyword(s):  
Molecular Graph ◽  
Topological Indices ◽  
Connectivity Index ◽  
Topological Properties ◽  
Benzenoid Hydrocarbons ◽  
Connectivity Indices

The Randić (product) connectivity index and its derivative called the sum-connectivity index are well-known topological indices and both of these descriptors correlate well among themselves and with the π-electronic energies of benzenoid hydrocarbons. The general n connectivity of a molecular graph G is defined as [Formula: see text] and the n sum connectivity of a molecular graph G is defined as [Formula: see text], where the paths of length n in G are denoted by [Formula: see text] and the degree of each vertex vi is denoted by di. In this paper, we discuss third connectivity and third sum-connectivity indices of diamond-like networks and compute analytical closed results of these indices for diamond-like networks.

Comparison Between Two Kinds of Connectivity Indices for Measuring the π-Electronic Energies of Benzenoid Hydrocarbons

2019 ◽  
Vol 74 (5) ◽  
pp. 367-370 ◽  
Author(s):  
Deqiang Chen
Keyword(s):  
Real Number ◽  
Molecular Descriptors ◽  
Connectivity Index ◽  
Benzenoid Hydrocarbons ◽  
The Real ◽  
Connectivity Indices ◽  
General Product

AbstractIn this paper, we show that both the general product-connectivity index χα and the general sum-connectivity index \({}^{s}{\chi_{\alpha}}\) are closely related molecular descriptors when the real number α is in some interval. By comparing these two kinds of indices, we show that the sum-connectivity index \({}^{s}{\chi_{-0.5601}}\) is the best one for measuring the π-electronic energies of lower benzenoid hydrocarbons. These improve the earlier results.

Molecular connectivity indices revisited

1990 ◽  
Vol 55 (3) ◽  
pp. 630-633 ◽  
Author(s):  
Milan Kunz
Keyword(s):  
Adjacency Matrix ◽  
Connectivity Index ◽  
Regular Graphs ◽  
Randić Index ◽  
Molecular Connectivity ◽  
Randic Index ◽  
Molecular Connectivity Indices ◽  
Connectivity Indices

It is shown that the product νiνj of degrees ν of vertices ij, incident with the edge ij, is the number of paths of length 1, 2, and 3 in which the edge is in the center. The unified connectivity index χm = Σ(νiνj)m, where the sum is made over all edges, with m = 1, is the sum of the number of edges, the Platt number and the polarity number. And it is identical with the half sum of the cube A3 of the adjacency matrix A. The Randić index χ-1/2 of regular graphs does not depend on their connectivity.

scholarly journals The General Connectivity and General Sum-Connectivity Indices of Nanostructures

2015 ◽  
Vol 44 ◽  
pp. 73-80
Author(s):  
Mohammad Reza Farahani
Keyword(s):  
Quantitative Structure Activity Relationship ◽  
Connectivity Index ◽  
Quantitative Structure ◽  
Structure Property ◽  
The Third ◽  
Structure Activity ◽  
New Variant ◽  
Connectivity Indices ◽  
Structure Property Relationship ◽  
Vertex Set

Let G be a simple graph with vertex set V(G) and edge set E(G). For ∀νi∈V(G),di denotes the degree of νi in G. The Randić connectivity index of the graph G is defined as [1-3] χ(G)=∑e=v1v2є(G)(d1d2)-1/2. The sum-connectivity index is defined as χ(G)=∑e=v1v2є(G)(d1+d2)-1/2. The sum-connectivity index is a new variant of the famous Randić connectivity index usable in quantitative structure-property relationship and quantitative structure-activity relationship studies. The general m-connectivety and general m-sum connectivity indices of G are defined as mχ(G)=∑e=v1v2...vim+1(1/√(di1di2...dim+1)) and mχ(G)=∑e=v1v2...vim+1(1/√(di1+di2+...+dim+1)) where vi1vi2...vim+1 runs over all paths of length m in G. In this paper, we introduce a closed formula of the third-connectivity index and third-sum-connectivity index of nanostructure "Armchair Polyhex Nanotubes TUAC6[m,n]" (m,n≥1).

Fifth Geometric-Arithmetic Index of Polyhex Zigzag TUZC6[m,n] Nanotube and Nanotori

2013 ◽  
Vol 3 (1) ◽  
pp. 191-196 ◽  
Author(s):  
Mohammad Reza Farahani
Keyword(s):  
Topological Index ◽  
Connectivity Index ◽  
Topological Descriptors ◽  
Degree Of A Vertex ◽  
Connectivity Indices ◽  
Topological Connectivity ◽  
Ga Index

Among topological descriptors, connectivity indices are very important and they have a prominent role in chemistry. The geometric-arithmetic index (GA) index is a topological index was defined as GA (G) in which degree of a vertex v denoted by dv. A new version of GA index was defined by A. Graovac et al recently, and is equale to GA (G) where GA (G) In this paper, we compute this new topological connectivity index for polyhex zigzag TUZC6[m,n] Nanotube and Nanotori.

The eccentric version of atom-bond connectivity index of tetra sheet networks

2018 ◽  
Vol 10 (05) ◽  
pp. 1850065 ◽  
Author(s):  
Muhammad Imran ◽  
Abdul Qudair Baig ◽  
Muhammad Razwan Azhar
Keyword(s):  
Connected Graph ◽  
Molecular Graph ◽  
Theoretical Chemistry ◽  
Connectivity Index ◽  
Maximum Distance ◽  
Eccentric Connectivity Index ◽  
Topological Descriptor ◽  
Degree Of A Vertex ◽  
Connectivity Indices ◽  
Atom Bond

Among topological descriptor of graphs, the connectivity indices are very important and they have a prominent role in theoretical chemistry. The atom-bond connectivity index of a connected graph [Formula: see text] is represented as [Formula: see text], where [Formula: see text] represents the degree of a vertex [Formula: see text] of [Formula: see text] and the eccentric connectivity index of the molecular graph [Formula: see text] is represented as [Formula: see text], where [Formula: see text] is the maximum distance between the vertex [Formula: see text] and any other vertex [Formula: see text] of the graph [Formula: see text]. The new eccentric atom-bond connectivity index of any connected graph [Formula: see text] is defined as [Formula: see text]. In this paper, we compute the new eccentric atom-bond connectivity index for infinite families of tetra sheets equilateral triangular and rectangular networks.

scholarly journals Sharp Bounds for the General Sum-Connectivity Indices of Transformation Graphs

2017 ◽  
Vol 2017 ◽  
pp. 1-7 ◽  
Author(s):  
Haiying Wang ◽  
Jia-Bao Liu ◽  
Shaohui Wang ◽  
Wei Gao ◽  
Shehnaz Akhter ◽  
...  
Keyword(s):  
Real Number ◽  
Line Graph ◽  
Connectivity Index ◽  
Point Graph ◽  
Total Graph ◽  
Sharp Bounds ◽  
Graph Transformations ◽  
Degree Of Vertex ◽  
Connectivity Indices ◽  
Distinct Transformation

Given a graph G, the general sum-connectivity index is defined as χα(G)=∑uv∈E(G)dGu+dGvα, where dG(u) (or dG(v)) denotes the degree of vertex u (or v) in the graph G and α is a real number. In this paper, we obtain the sharp bounds for general sum-connectivity indices of several graph transformations, including the semitotal-point graph, semitotal-line graph, total graph, and eight distinct transformation graphs Guvw, where u,v,w∈+,-.

Further results on Zagreb eccentricity coindices

2020 ◽  
Vol 12 (06) ◽  
pp. 2050075
Author(s):  
Mahdieh Azari
Keyword(s):  
Wiener Index ◽  
Connectivity Index ◽  
Lower And Upper Bounds ◽  
Graph Invariants ◽  
Eccentric Connectivity Index ◽  
Size Number ◽  
Connectivity Indices ◽  
Degree Distance ◽  
Graph Parameters ◽  
Eccentric Distance

The eccentric connectivity index and second Zagreb eccentricity index are well-known graph invariants defined as the sums of contributions dependent on the eccentricities of adjacent vertices over all edges of a connected graph. The coindices of these invariants have recently been proposed by considering analogous contributions from the pairs of non-adjacent vertices. Here, we obtain several lower and upper bounds on the eccentric connectivity coindex and second Zagreb eccentricity coindex in terms of some graph parameters such as order, size, number of non-adjacent vertex pairs, radius, and diameter, and relate these invariants to some well-known graph invariants such as Zagreb indices and coindices, status connectivity indices and coindices, ordinary and multiplicative Zagreb eccentricity indices, Wiener index, degree distance, total eccentricity, eccentric connectivity index, second eccentric connectivity index, and eccentric-distance sum. Moreover, we compute the values of these coindices for two graph constructions, namely, double graphs and extended double graphs.

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