O kanonskom označavanju ugljikovih atoma u fullerenima: C60 buckminsterfulleren

Numbering of atoms in relatively large molecules, such as fullerenes appears for most part to be arbitrary or based on ad hoc schemes. We argue in favor of the use of a particular canonical labeling of atoms in molecules based on the smallest possible binary molecular code obtained from the adjacency matrix when its rows are read from left to right and from top to bottom. The approach has been illustrated with buckminsterfullerene. We have outlined advantages of the approach and have shown that finding canonical labels is practical even in the case of large regular graphs.Označavanje atoma u velikim i složenim molekulama vrlo je često proizvoljno ili je zasnovano na ad hoc shemama. Preporuča se novo i sustavno označavanje atoma u molekulama koje se temelji na najmanjem mogućem binarnom molekularnom kodu. Čitanje matrice susjedstva grafa molekule po retcima definira binarni molekularni kod: najmanji među njima se zove kanonski kod. Na primjeru molekule buckminsterfullerena pokazano je kako se može odrediti ovaj kod. Istaknute su prednosti novoga načina označavanja atoma u velikim molekulama a posebice za one prikazane regularnim grafovima

Topological Properties of Small Li Clusters and the Pariser-Parr-Pople-Type Model

A simple analysis of the spin multiplicity of the ground state is presented in the weakly correlated limit. The ab initio MRD-CI predictions on the small lithium clusters and the full CI results of the Pariser-Parr-Pople model for the corresponding network of centers exhibit a close parallelity which is possible to rationalize

MATH/CHEM/COMP \u2799

MATH/CHEM/COMP \u2799 (MCC\u2799), the Fourteenth Dubrovnik International Course & Conference on the Interfaces between Mathematics, Chemistry and Computer Sciences, was held at the Inter-University Centre, in Dubrovnik, Croatia, on June 21-26, 199

MATH/CHEM/COMP \u2799

MATH/CHEM/COMP \u2799 (MCC\u2799), the Fourteenth Dubrovnik International Course & Conference on the Interfaces between Mathematics, Chemistry and Computer Sciences, was held at the Inter-University Centre, in Dubrovnik, Croatia, on June 21-26, 199

On the Concept of Molecular Complexity

The previous measures of the complexity of graphs, and thence molecular graphs, have been mainly based on the information content of graphs. We argue here that the two concepts, the information content of a graph and the graph complexity, are distinctive and should be differentiated. We propose a new index of molecular complexity which takes into account not only the connectivity and the closely associated structural features of molecular structure (e.g., branching, cyclicity) but also the symmetry of a molecule as the basis for the partitioning of molecular components considered for construction of the complexity measure of a graph

Precipitation and Characterization of Strontium Phosphates

Spontaneous precipitation of strontium phosphates was studied over a wide concentration range of strontium chloride (2 · 10-4 -- 8 · 10-1 mol dm-3) and of sodium phosphate (4 · 10·4 ·-3 · 10 1 mol dm-3) solutions. In all systems, initial pH was 7.4 and sodum chloride concentration w<•.s 0.15 mol dm-3• The precipitates aged for 1 day and 30 days at 298 K and 310 K were characterized by light microscopy and X-ray powder diffraction. Solid phases SrHP04 (a and P modifications), Sr.10 (P04)s (OHh, Ha Sra (P04);; · · 2H20, and Na [Sr (H20)u] PQ4 were determined .. According to the precipitation boundary after 30 days (equilibrium conditions) the solubility product of Na [Sr (H20)9] P04 is determined as follows: log ([Na+] [Sr2+] [Po4-3]) = -9.98±0.11 (at I = 0.25 mol dm-3, 298 K)

Chemical Graph Theory. V. On the Classification of Topological Biradicals

We have considered skeletal forms for topological (conjugated) biradicals and have examined alternative structural classification schemes for them. In particular, we have looked more closely at the classification proposed by Herndon and Ellzey, based on the multiplicity of the zero eigenvalue and have examined all acyclic forms having 12 or fewer carbon atoms, and all cyclic forms having 8 or fewer carbon atoms. Whlle the present work does not contribute to resolving the controversy as to which type of biradical can be expected to have the singlet, and which the triplet ground state, it provides the possibility of grouping compounds of the same expected ground state and thus allows the deduction of similar properties for members of the same group. Hence, definitive theoretical or experimental results obtained for a new standard species can then be applied to a wider body of biradicals. Examination of the distribution of »unpaired« spin density and the character of bonds which have a constant body type (so-called essentially single or essentially double CC bonds) provided guidance for deriving a number of rules for the construction of larger topological biradical forms by the combination (as fragments) of smaller-sized biradicals or other molecular fragments