Anchoring the potential energy surface of the diacetylene dimer

Abstract

The diacetylene dimer, (H–C≡C–C≡C–H)₂, serves as a useful prototype for delocalised π-type interactions. It mimics many of the important characteristics of aromatic π-stacking prototypes such as (C₆H₆)₂ but is small enough that full geometry optimisations and vibrational frequency computations with analytic derivatives are feasible with sophisticated electronic structure techniques. Six stationary points on the potential energy surface (PES) of (H–C≡C–C≡C–H)₂ have been identified and characterised with CCSD(T) computations. The relative energies of the stationary points on each PES have been anchored by combining explicitly correlated MP2-R12 computations with corrections for higher-order correlation effects as well as core correlation effects. These computations identify a Y-shaped global minimum with an electronic dissociation energy (D _e ) of 1.84 kcal mol⁻¹ at the all-electron CCSD(T) complete basis set limit. Higher-order correlation corrections are necessary to correctly identify the global minimum while core correlation effects have almost no influence on the relative energies of the stationary points.

Keywords:

• potential energy surface
• diacetylene dimer
• π-type interactions

Acknowledgements

The authors would like to thank the Mississippi Center for Supercomputing Research for access to their resources. Financial support for this work was provided, in part, from the National Science Foundation (EPS-0132618, CHE-0517067).