Exploration of potential and free energy surfaces of the neutral Be$_4$B$_{8}$ chiral clusters and their stabilities at finite temperatures

TL;DR

This study investigates the potential and free energy surfaces of Be4B8 chiral clusters at finite temperatures, incorporating entropic effects and exploring their structural and spectral properties using advanced computational methods.

Contribution

It introduces a multilevel genetic algorithm coupled with DFT to explore cluster structures and assesses their thermodynamic stability and spectra at finite temperatures.

Findings

Identification of low-energy isomers and their Boltzmann-weighted spectra.

Discovery of a temperature-induced switch from endergonic to exergonic reactions at 739 K.

Comparison of DFT and CCSD(T) energetic orderings.

Abstract

The lowest-energy structure, distribution of isomers, and their molecular properties depend significantly on the geometry and temperature. The total energy computations under DFT methodology are typically carried out at zero temperature; thereby, entropic contributions to total energy are neglected, even though functional materials work at finite temperature. In the present study, the probability of occurrence of one particular Be$_4$B$_8$ isomer at temperature T is estimated within the framework of quantum statistical mechanics and nanothermodynamics. To locate a list of all possible low-energy chiral and achiral structures, an exhaustive and efficient exploration of the potential/free energy surface is done by employing a multilevel multistep global genetic algorithm search coupled to DFT. Moreover, 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 computed VCD/IR spectrum of each isomer is multiplied by their corresponding Boltzmann weight at temperature T; then, they are summed together to produce a final Boltzmann weighted 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.