Efficient parallel implementation of response theory: Calculations of the second hyperpolarizability of polyacenes

We describe an efficient parallel implementation of response theory for calculations of molecular properties, and demonstrate its performance by calculations on a series of polyacene molecules, from benzene to hexacene. The polarizability and the second hyperpolarizability of the molecules in this series are found to scale as N-1.4 and N-3.5 respectively, where N is the number of benzene rings in the molecule. These N-dependences are weaker than those predicted for the linear polyenes.