Effect of Chemical Order in the Structural Stability and Physicochemical Properties of B12N12 Fullerenes

Alejandro Escobedo-Morales,José Humberto Camacho-García,Diego Cortes-Arriagada,Lorenzo Tepech-Carrillo,Alejandro Bautista-Hernández,Ernesto Chigo-Anota

doi:10.1038/s41598-019-52981-1

Abstract

The effect of chemical order in the structural and physicochemical properties of B12N12 [4,6]-fullerene (BNF) isomers was evaluated using density functional theory and molecular dynamic calculations. The feasibility to find stable BNF isomers with atomic arrangement other than the well-known octahedral Th-symmetry was explored. In this study, the number of homonuclear bonds in the modeled nanostructures was used as categorical parameter to describe and quantify the degree of structural order. The BNF without homonuclear bonds was identified as the most energetically favorable isomer. However, a variety of BNF arrays departing from Th-symmetry was determined as stable structures also. The calculated vibrational spectra suggest that isomers with chemical disorder can be identified by infrared spectroscopy. In general, formation of homonuclear bonds is possible meanwhile the entropy of the system increases, but at expense of cohesive energy. It is proposed that formation of phase-segregated regions stablishes an apparent limit to the number of homonuclear bonds in stable B12N12 fullerenes. It was found that formation of homonuclear bonds decreases substantially the chemical hardness of BNF isomers and generates zones with large charge density, which might act as reactive sites. Moreover, chemical disorder endows BNF isomers with a permanent electric dipole moment as large as 3.28 D. The obtained results suggest that by manipulating their chemical order, the interaction of BNF’s with other molecular entities can be controlled, making them potential candidates for drug delivery, catalysis and sensing.

Highlights

Boron nitride (BN) compound has gained huge attention because its high mechanical hardness, thermochemical stability, and electric and thermal conductivity
Because deeper understanding of chemical order may contribute to achieve fine-tuning of molecular functions, the aim of this study is to explore from a theoretical perspective the feasibility to find stable B12N12 [4,6]-fullerene isomers with atomic arrangement other than the octahedral Th-symmetry, if so, quantify the effect of chemical order in their structural and physicochemical properties
The effect of chemical order in the structural and physicochemical properties of B12N12 [4,6]-fullerene (BNF) isomers was studied from a theoretical perspective using density functional theory and molecular dynamic calculations

Summary

Introduction

Boron nitride (BN) compound has gained huge attention because its high mechanical hardness, thermochemical stability, and electric and thermal conductivity. From computational ab initio calculations at the MP2/ DZP level, they determined that among them, that with truncated octahedron symmetry (point group: Th) has the lowest total energy This [4,6]-fullerene has 14 faces generated by 36 covalent bonds between B and N atoms with sp[2] hybridization. Because deeper understanding of chemical order may contribute to achieve fine-tuning of molecular functions, the aim of this study is to explore from a theoretical perspective the feasibility to find stable B12N12 [4,6]-fullerene isomers with atomic arrangement other than the octahedral Th-symmetry, if so, quantify the effect of chemical order in their structural and physicochemical properties. There is one unique arrangement of atoms to obtain a B12N12 [4,6]-fullerene (BNF) having Th-symmetry This B12N12 conformational isomer has no homonuclear bonds[15]. The chemical order index σ for the BNF isomers was defined as:

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Conclusion