A Fresh Look at Resonances and Complex Absorbing Potentials: Density Matrix-Based Approach.
A new strategy of using complex absorbing potentials (CAPs) within electronic structure calculations of metastable electronic states, which are ubiquitous in chemistry and physics, is presented. The stumbling block in numerical applications of CAPs is the necessity to optimize the CAP strength for each system, state, and one-electron basis set, while there is no clear metric to assess the quality of the results and no simple algorithm of achieving numerical convergence. By analyzing the behavior of resonance wave functions, we found that robust results can be obtained when considering fully stabilized resonance states characterized by constant density at large η (parameter determining the CAP strength). Then the perturbation due to the finite-strength CAP can be removed by a simple energy correction derived from energy decomposition analysis and response theory. The utility of this approach is illustrated by CAP-augmented calculations of several shape resonances using EOM-EA-CCSD with standard Gaussian basis sets.
†Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.
Thomas-C
TC
Jagau
†Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.
Dmitry
D
Zuev
‡Department of Chemistry, Boston University, Boston, Massachusetts 02215-2521, United States.
Ksenia B
KB
Bravaya
†Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.|§Department of Chemistry, University of California, Berkeley, California 94720, United States.|∥Q-Chem Inc., 6601 Owens Drive, Suite 105, Pleasanton, California 94588, United States.
Evgeny
E
Epifanovsky
†Department of Chemistry, University of Southern California, Los Angeles, California 90089-0482, United States.
Anna I
AI
Krylov
equation-of-motion coupled-cluster methods; metastable states; resonances