Low‐energy structures of benzene clusters with a novel accurate potential surface

Abstract

The benzene-benzene (Bz-Bz) interaction is present in several chemical systems and it is known to be crucial in understanding the specificity of important biological phenomena. In this work, we propose a novel Bz-Bz analytical potential energy surface which is fine-tuned on accurate ab initio calculations in order to improve its reliability. Once the Bz-Bz interaction is modeled, an analytical function for the energy of the Bzn clusters may be obtained by summing up over all pair potentials. We apply an evolutionary algorithm (EA) to discover the lowest-energy structures of Bzn clusters (for n=2-25), and the results are compared with previous global optimization studies where different potential functions were employed. Besides the global minimum, the EA also gives the structures of other low-lying isomers ranked by the corresponding energy. Additional ab initio calculations are carried out for the low-lying isomers of Bz3 and Bz4 clusters, and the global minimum is confirmed as the most stable structure for both sizes. Finally, a detailed analysis of the low-energy isomers of the n = 13 and 19 magic-number clusters is performed. The two lowest-energy Bz13 isomers show S6 and C3 symmetry, respectively, which is compatible with the experimental results available in the literature. The Bz19 structures reported here are all non-symmetric, showing two central Bz molecules surrounded by 12 nearest-neighbor monomers in the case of the five lowest-energy structures.

Adsorption of molecular hydrogen on coronene with a new potential energy surface

“…The choice of the MP2C approach relies on its capability to provide accurate estimations for the interaction energies in weakly bound noncovalent systems, ranging from RG-coronene 37 or benzene-benzene 41 up to moleculeannulenes [42][43][44] , at an affordable computational cost. DFT-SAPT estimations of the interaction energies are in general more expensive in terms of computing time, but they have been also performed in order to provide alternative results of well known reliability 45,46 and unaffected by the basis set superposition error (BSSE).…”

Noncovalent interactions between cisplatin and graphene prototypes

“…Benchmark interaction energies between CP and pyrene have been computed at the “coupled” supermolecular second‐order Møller–Plesset perturbation theory (MP2C) level of theory. Our choice to use the MP2C approach relies on its capability to provide accurate estimations for weakly bound systems ranging from benzene–benzene to rare gas–graphene prototypes and molecule–graphene derivatives at an affordable computational cost. For a proper estimation of the involved noncovalent interactions, the use of large basis sets (including diffuse functions) is required.…”

A global optimization perspective on molecular clusters

“…In a recent work [31], we proposed a new accurate Bz-Bz interaction potential to obtain low-energy structures (including the global minimum) of benzene clusters up to n = 25 by employing the EA. In the case of small aggregates, we recalculated the low-lying minima at the MP2C/CBS level of theory [56]: the four low-energy minima of Bz 3 follow the same order as for the empirical potential, and the Bz 4 global minimum was also confirmed [31]. As in previous studies [32,57] with less accurate potentials [58,59], structures with special stability compared with their neighbour-sizes (so-called 'magic numbers') arise at n = 13, 19 and 23, which appears to be related to the number of Bz molecules surrounded by a maximum of 12 nearest-neighbours [31,57]; nonetheless, these potentials show different structures for several cluster sizes.…”