Direct molecular dynamics using quantum chemical hamiltonians: C₆₀ impact on a passive surface

Quantum chemical Hamiltonians of the semiempirical type potentially provide a more reliable description of a potential energy surface for large scale molecular dynamics than does the tight-binding (TB) Hamiltonian, a reparametrized extended Hückel Hamiltonian including a short range repulsion. Their performance is tested here and compared with results from TB simulations. The methods considered are from the zero differential overlap family of semiempirical Hamiltonians, these are the intermediate neglect of differential overlap (INDO) method and three parametrizations of the neglect of differential diatomic overlap (NDDO) method, AM1, PM3, and MNDO. The collision of the C₆₀ molecule with a passive surface at two collision energies is the test problem, where the higher energy leads to shattering of the molecule. The NDDO Hamiltonians are found to give a better qualitative description than the INDO Hamiltonian at both energies and further studies to reparametrize the NDDO form for direct MD are indicated.