Development of alternative, screening based, local Cpupled Cluster methods and efficient algorithms for parallel architectures

点击翻译按钮获取中文摘要

In the field of Coupled Cluster method development for larger molecular systems a gap has been opening during recent years between the robust and highly accurate conventional methods and the local approximations that suffer from a certain arbitrariness in the truncation scheme based on local orbitals and excitation domains. The dynamical thresholding algorithm developed in our group represents an alternative to the linear scaling methods that focuses on accuracy and error-control rather than on efficiency. In previous work it has been shown that using perturbation theory to prescreen amplitudes leads to a Coupled Cluster approximation with controllable error that does not require any a priori assumptions about the structure of the wavefunction parameters. The project presented in this proposal aims at turning the current pilot implementation into a fully efficient scheme for parallel computer architectures. For this purpose the current screening techniques have to be applied to the intermediate quantities that occur in Coupled Cluster algorithms. In order to reach the break even point of the new, low scaling algorithm to highly efficient conventional Coupled Cluster implementations it is necessary to exploit the computational resources of large scale parallel computer architectures. For the efficient development of a new implementation automatic program generation techniques will be used. Finally the features of the code will be extended to energy gradients and the treatment of higher levels of excitations.