Department of Chemistry
A headshot

Danny Yeager

Department of Chemistry
Texas A&M University
College Station, TX 77843-3255

P: 979-845-3436
F: 979-845-4719

Researcher ID

Current Activities

Our research in theoretical chemistry is currently focused in the development and study of new methods for electronic structure and for molecular ionization.

In electronic structure we are primarily concerned with the formulation of new Green's function methods for the direct calculation of electron affinities, ionization potentials, excitation energies, electronic transition probabilities, and other response properties. With one-particle Green's function methods, energy differences between an initial state and states with one additional or one less electron are calculated directly. That is, vertical ionization potentials or electron affinities are obtained. Similarly, with two-particle Green's function methods excitation energies or double ionization potentials and double electron affinities are determined. These methods are contrasted with the more traditional wave function based methods where total electronic energies and corresponding wavefunctions are calculated and the energy differences (which are what's usually measured in the laboratory) are obtained by subtracting one fairly large number from another to obtain the observed smaller quantity.

We have proposed and developed new Green's function techniques which are inherently based on multiconfigurational initial states. Furthermore, our techniques can be used for open shell as well as closed shell initial states. These are in contrast with the more usual Green's function approaches which require a closed shell single configuration initial state corrected using Møller-Plesset perturbation theory. Our single-particle Green's function approach is known as the multiconfigurational spin tensor electron propagator method (MCSTEP); our two-particle approach for double ionization potentials and electron affinities is called the multiconfigurational particle-particle propagator method (MCP2P); and our two-particle approach for excitation energies is known as multiconfigurational linear response or multiconfigurational time dependent Hartree-Fock (MCLR/MCTDHF).

We are also developing new ways for theoretically describing photoionization and electron-impact ionization. These methods involve joining our Green's function methods with other techniques for determining cross sections.

Educational Background

B. S., 1968, University of Iowa

Ph. D., 1975, California Institute of Technology

Research Associate, 1975-77, University of Chicago

Selected Publications

  • "An Electron Propagator Method with a Multiconfigurational Second-Order Perturbation Theory (CASPT2) Wavefunction as the Initial State in the Fermion Block," Dodi Heryadi and Danny L. Yeager, Journal of Chemical Physics 114, 5124-5136 (2001).
  • "Purely Theoretical Electron-Impact Ionization Cross Sections of Silicon Hydrides and Silicon Fluorides Obtained from Explicitly Correlated Methods," N.O.J. Malcolm and Danny L. Yeager, Journal of Chemical Physics 113, 8-17 (2000).
  • "Resolving the Controversy Over NO3, the Second Ionization Potential of the Nitrate Free Radical," Dodi Heryadi and Danny Yeager, Journal of Chemical Physics 112, 4572-4578 (2000).