Accelerating the convergence of higher-order coupled-cluster methods II: coupled-cluster ? equations and dynamic damping

The method of sub-iteration, which was previously applied to the higher-order coupled-cluster amplitude equations, is extended to the case of the coupled-cluster ? equations. The sub-iteration procedure for the ? equations are found to be highly similar to that for the amplitude equations, and to exhibit a similar improvement in the rate of convergence relative to extrapolation of all or amplitudes using DIIS. A method of dynamic damping is also presented which is found to effectively recover rapid convergence in the case of oscillatory behaviour in the amplitude or ? equations. Together, these techniques allow for the convergence of both the amplitude and ? equations necessary for the calculation of analytic gradients and properties of higher-order coupled-cluster methods without the high memory or disk I/O cost of full DIIS extrapolation. [GRAPHICS] .