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Analytical second derivatives in the Amsterdam density functional package



Recently, analytical second derivatives with respect to nuclear coordinates have been implemented in the Amsterdam density functional (ADF) package. This article presents the detailed formalism of that implementation. Calculations on small molecules such as methane show good agreement between the analytical and numerical frequencies. Calculations on benzene and larger molecules show that the analytical second derivatives code is 2 to 3 times faster than the numerical. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005