Abstract
Lowest-energy structures, the distribution of isomers, and their molecular properties depend significantly on geometry and temperature. Total energy computations using DFT methodology are typically carried out at a temperature of zero K; thereby, entropic contributions to the total energy are neglected, even though functional materials work at finite temperatures. In the present study, the probability of the occurrence of one particular Be4B8 isomer at temperature T is estimated by employing Gibbs free energy computed within the framework of quantum statistical mechanics and nanothermodynamics. To identify a list of all possible low-energy chiral and achiral structures, an exhaustive and efficient exploration of the potential/free energy surfaces is carried out using a multi-level multistep global genetic algorithm search coupled with DFT. In addition, we discuss the energetic ordering of structures computed at the DFT level against single-point energy calculations at the CCSD(T) level of theory. The total VCD/IR spectra as a function of temperature are computed using each isomer’s probability of occurrence in a Boltzmann-weighted superposition of each isomer’s spectrum. Additionally, we present chemical bonding analysis using the adaptive natural density partitioning method in the chiral putative global minimum. The transition state structures and the enantiomer–enantiomer and enantiomer–achiral activation energies as a function of temperature evidence that a change from an endergonic to an exergonic type of reaction occurs at a temperature of 739 K.
Highlights
The potential of boron atoms to form stable molecular networks [1,2] lies in the fact that they have three valence electrons and four available orbitals, which implies they are electron-deficient
Our results show that the chirality on Be4 B8 arises from Be–Be dimers capping the boron ring; the lowest energy chiral structure is favored by the interaction between beryllium and the boron framework
We have estimated the probability of occurrence of each isomer of the Be4 B8 cluster under the framework of nanothermodynamics
Summary
The potential of boron atoms to form stable molecular networks [1,2] lies in the fact that they have three valence electrons and four available orbitals, which implies they are electron-deficient. Since molecular properties depend greatly on their geometry [32,33], boron clusters exhibit a large number of molecular properties that have potential applications in medicine [34,35,36,37], molecular motors [21,23,38], superhard materials [39], hydrogen storage [40], batteries [41,42,43,44], catalysis [45], and energy materials [46], among many others These nanoclusters have attracted attention due to their chiroptical properties, potential applications in efficient chiral discrimination [47,48], nonlinear optics [49], and potential to create chiral materials with interesting properties [13,50,51], not to mention the fact that chiral structures play a decisive role in biological activity [52]. Together with experimental photoelectron spectroscopy, have reported the first pure boron chiral B30 − structure as the putative global minimum [13] In these pairs of planar enantiomers, chirality arises due to the hexagonal hole and its position.
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