Difficulties and Virtues in Assessing the Potential Energy Surfaces of Carbon Clusters via DMBE Theory: Stationary Points of C_κ (κ = 2–10) at the Focal Point

Abstract

The previously reported potential energy surfaces (PESs) of ground-state singlet C3 and triplet C4 are here utilized as input for the construction of approximate cluster expansions for larger Cκ (κ = 5–10) species. Relying primarily on the double many-body expansion (DMBE) approach, global potentials are obtained by summing the total interaction energies of all atomic subclusters up to four-body terms. The notable capability of the final forms in predicting good estimates of the linear global minima and their thermochemical/structural properties may provide important insights into the structure-determining nature of the (2 + 3 + 4) terms. The main difficulties and virtues in assessing Cκ’s via DMBE theory are analyzed and new prospects given for the construction of global reliable PESs for the target species.

From six to eight Π-electron bare rings of group-XIV elements and beyond: can planarity be deciphered from the “quasi-molecules” they embed?

“…Interestingly, the present results may also explain why the MBE of pentatomic or larger molecules should not be truncated before four-body energy terms when predicting their global potentials, as done for up to 10-atom carbon clusters. 158 Although successfully scrutinized in the above as well as further, even larger, neutral [ n ]annulenes and annulenic anions that satisfy the (4 n + 2) Hückel rule (and other molecules not addressed here), it is too early to say that exceptions cannot emerge. Indeed, examples have been reported in the current work where planarity vs. nonplanarity indices may come to a tie (see Fig.…”

Análise computacional da estabilidade de compostos atípicos de carbono aplicada à astroquímica

“…[4]). Para além disso, muitos dos sistemas referidos apresentam cruzamentos de curvas e superfícies de energia potencial que um tratamento mais rigoroso deve considerar [3][4][5]. Para além deste método variacional, foi usado um método perturbativo, o Møller-Plesset de 2 a ordem (MP2).…”

“…Mais recentemente, Varandas e colaboradores (veja Refs. [3][4][5]) têm feito cálculos muito precisos para estes agregados, realçando os cruzamentos de superfícies que estes envolvem e também como protótipos de métodos de escalamento das bases de funções usadas e de cálculo e representação de superfícies de energia potencial [5,6]. Várias revisões foram publicadas sobre este tema [3] e, em particular, sobre a sua importância no que concerne à astroquímica [7].…”

Cubic Octa-Carbon: Quantum-Chemical Design of Molecular Structure and Potential Way of Its Synthesis from Cubane

“…This substance can serve as a very useful precursor for the organic synthesis of a number of cubane derivatives, for example, polycyclic framework compounds containing articulated cubane fragments; seems to be very promising for use in a number of branches of technology, in particular, as “building blocks” for new nanodevices, which, in turn, can be implemented to create digital memory systems; the possibility of using it in the creation of catalysts for various physicochemical processes is not excluded. The synthesis of such a compound, however, has not yet been experimentally carried out; though there are many works devoted to the theoretical calculation of its molecular and/or electronic structure, carried out mainly using DFT, HF, or even semiempirical methods (see, in particular, [ 18 , 19 , 20 , 21 , 22 , 23 , 24 , 25 , 26 , 27 , 28 , 29 , 30 , 31 , 32 ]). In this regard, the purpose of this work is to perform a quantum-chemical calculation of the molecular structure of this compound by a more rigorous ab initio quantum-chemical method, namely CCSD (T)/QZVP, as well as to theoretically consider the possibility of its synthesis based on a chemical compound that also has cubic structure, namely, cubane C 8 H 8 .…”