**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.**