First-principles molecular-dynamics simulations for neutral p-chloranil and its radical anion

The neutral p-chloranil (2,3,5,6-tetrachloro-p-benzoquinone) and its radical anion have been extensively studied using the Car-Parrinello projector augmented wave method, which is an all-electron electronic structure method for first-principles molecular dynamics based on the local density approximation of density functional theory. Frequencies and eigenmodes are derived by fitting a system of harmonic oscillators to the molecular-dynamics trajectories. The dependence of the bond lengths and vibrational frequencies on the molecular ionicity is discussed, and the electron affinity, Coulomb repulsion, and the spin-splitting parameter of p-chloranil are also derived.