Convergence improvement for coupled cluster calculations
Authors: N. Mosyagin (Petersburg Nuclear Physics Institute), E. Eliav,
U. Kaldor (Tel Aviv
University)
Comments: 7 pages, IOPP style
Subj-class: Chemical Physics
Convergence problems in coupled-cluster
iterations are discussed, and a new iteration
scheme is proposed. Whereas the Jacobi
method inverts only the diagonal part of the
large matrix of equation coefficients,
we invert a matrix which also includes a relatively
small number of off-diagonal coefficients,
selected according to the excitation
amplitudes undergoing the largest change
in the coupled cluster iteration. A test case
shows that the new IPM (inversion of partial
matrix) method gives much better
convergence than the straightforward Jacobi-type
scheme or such well-known
convergence aids as the reduced linear
equations or direct inversion in iterative
subspace methods.