Calculating Infrared Intensities

Jeff Stephens

Contents

 

     Introduction

     Integrated absorptivity

     Separation of Motion

          Defining a New Coordinate System

          Deriving the Kinetic Energy

          The Eckart-Sayvetz conditions

     Theoretical Intensities

          Theoretical equation for intensity

          Isotopic Effects

     Implementation Using Psi

     Determining Vibrational Frequencies and Intensities via Finite Displacements

     for CI and CC Computations

          Preprocessing

          Generate Displacements

          Check Equilbrium Geometry in Lower Symmetries

          Calculating Derivatives and Dipole Moments

          Create Composite file11 and file28

          Transform the Gradients in Cartesian Coordinates to Internal Coordinates

          Calculate Dipole Moment First Derivatives in Internal Coordinates (for Intensities)

          Transforming Dipole Moment Derivatives from Internals to Cartesians

          Generate the Second Derivatives of the Energy in Internal Coordinates

          Transforming the Second Derivatives of the Energy into Cartesian and

          Calculation of the Frequencies and Intensities

          Obtaining Force Constants (Optional)

          Finit2freq: An easier method? (Optional)

          Isotopic Substitution (Optional)

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