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1. Quantum Chemistry

   Linked via "nuclear coordinates"

   Quantum Chemical Results and Molecular Geometry
   A primary application of quantum chemistry is the determination of molecular structure and energetic minima on the PES. At a stationary point on the PES, the forces on all nuclei are zero, meaning the gradient of the energy with respect to nuclear coordinates is zero:
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2. Quantum Chemistry

   Linked via "nuclear coordinates"

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   The nature of this stationary point (minimum, transition state, or higher-order saddle point) is determined by analyzing the Hessian matrix, which contains the second derivatives of the energy with respect to nuclear coordinates. The number of negative eigenvalues in the Hessian matrix corresponds to the number of imaginary vibrational frequencies. For a true minimum, there must be zero ima…