Ab-Initio Molecular Dynamics of Organic Compounds on a Massively Parallel Computer

We present results of ab-initio electronic structure calculations and molecular dynamics simulations of organic molecules carried out using adaptive curvilinear coordinates, within the local density approximation of density functional theory. This approach allows for an accurate treatment of first-row elements, which makes it particularly suitable for investigations of organic compounds. A recent formulation of this method relies on a real-space approach which combines the advantages of finite-difference methods with the accuracy of adaptive coordinates, and is well suited for implementation on massively parallel computers. We used molecular dynamics simulations to obtain the fully relaxed structures of nitrosyl fluoride (FNO), and of the aromatic heterocycles furan and pyrrole. The equilibrium geometries obtained show excellent agreement with experimental data. The harmonic vibrational frequencies of furan and pyrrole were calculated by diagonalization of their dynamical matrix and are found to agree with experimental data within an rms error of 25 cm-1 and 28 cm-1 for furan and pyrrole respectively. This accuracy is comparable to that attained for smaller organic molecules using elaborate quantum chemistry methods.