Benzene trimer and benzene tetramer: Structures and properties determined by the nonempirical model (NEMO) potential calibrated from the CCSD(T) benzene dimer energies

Abstract

The energetics and structure of the benzene trimer and tetramer are investigated with the nonempirical model (NEMO) potential calibrated to high precision by comparison with CCSD(T) benzene dimer energies. From the obtained potential energy surface, possible configurations could be determined and the experimental observed structures could be identified. This potential also reproduces the binding energies and allows for the determination of all intermolecular modes. It could be shown that this potential is therefore well suited and important to predict the structure and thermodynamic data for larger clusters, which cannot be accurately computed by ab initio quantum chemical methods.

S 1 –S vibronic spectra of benzene clusters revisited. I. The tetramer

“…Theoretical studies on the trimer have predicted that the most stable structure has cyclic geometry where three benzenes are arranged so as to form an equilateral triangle. 29,39,48,57,59,63 This structure is consistent with IDSRS results reported by Felker's group. 50,53 Here we shall briefly describe their experimental method since this information is necessary to discuss our results.…”

“…Recently Engkvist et al have calculated the stabilization energy of the tetramer in several different structures with a more sophisticated nonempirical model ͑NEMO͒ potential based on coupled-cluster single double triple ͓CCSD͑T͔͒ calculations of the dimer. 59 The most stable structure seems to have a geometry similar to that of van de Waal. On the contrary to these results, an IDSRS study of the tetramer associated with intramolecular modes has suggested that the four benzene sites are inequivalent.…”

“…53 To reconcile this disagreement between theory and experiments, Engkvist et al speculated that the next stable isomer would be populated preferentially in the experiments because of a favor in entropy and a kinetic constraint. 59 With the aim to clarifying the above-mentioned obscurities around the benzene clusters, especially larger than dimer, we have reinvestigated the S 1 -S 0 transitions by observing mass-selective R2PI-deteced excitation and UV-UV hole burning spectra. Spectra of various isotopomer channels have been recorded in the expansion of mixtures of perprotonated and perdeuterated benzenes, and detailed comparison of them has shown that R2PI spectra obtained by monitoring the trimer isotopomers are affected by efficient fragmentation after ionization even when the two-color excitation is applied.…”

“…This result has been interpreted as a strong evidence for the cyclic structure, because the trimer is expected to be rigid relative to other clusters studied. 59 Krause et al measured the ionization potentials of the benzene clusters, and the binding energies of the clusters were evaluated by using the data. 43 It should be noted that the measurements of the ionization potentials for (benzene) n (nϭ2 -5) were preformed by monitoring the (benzene) n ϩ mass channels, respectively.…”

Excitonic couplings and electronic coherence in bridged naphthalene dimers

“…Extensive study of benzene has been carried out as well. Recent interest focused on the structure and properties of benzene clusters (30)(31)(32)(33)(34)(35)(36). Isotopically mixed benzene clusters have been used in the investigation of intermolecular interactions.…”