Energy gradient calculations

Open-Shell Analytic Gradients Implementation of the Direct Product Decomposition Approach in Energy Gradient Calculations. 

J. Gauss, J. F. Stanton, and R. J. Bartlett, ]. Chem. Phys., 95, 2623 (1991). Coupled-Cluster Open-Shell Analytic Gradients Implementation of the Direct Product Decomposition Approach in Energy Gradient Calculations. 

We will next show a few examples of reactions for which the determination and analysis of IRC characteristics have been carried out with the ab initio energy gradient calculation. 

Dapprich S, 1 Komiromi, K S By un, K Morokuma and M J Frisch 1999. A New ONIOM Implementation in Gaussian 98. Part I. The Calculation of Energies, Gradients, Vibrational Frequencies and Electric Field Derivatives. THEOCHEM 461-462 1-21. 

In addition to total energy and gradient, HyperChem can use quantum mechanical methods to calculate several other properties. The properties include the dipole moment, total electron density, total spin density, electrostatic potential, heats of formation, orbital energy levels, vibrational normal modes and frequencies, infrared spectrum intensities, and ultraviolet-visible spectrum frequencies and intensities. The HyperChem log file includes energy, gradient, and dipole values, while HIN files store atomic charge values. 

I will use the term gradient method to imply the existence of an analytical formula for the calculation of an energy gradient. In order to calculate an analytical formula, we have to be able to differentiate one- and two-electron integrals jWith respect to nuclear coordinates. 

B. Calculations of Potential Energy Gradient at or Near the Starting Geometry... 

Fig. 4. Physical significance of calculations of the potential energy gradient at the starting nuclear geometry. From left to right, negative slope, positive slope, and a calculation for the second excited state...

---