Types of Coupled-cluster Methods
The classification of traditional coupled-cluster methods rests on the highest number of excitations allowed in the definition of . The abbreviations for coupled-cluster methods usually begin with the letters "CC" (for coupled cluster) followed by
- S - for single excitations (shortened to singles in coupled-cluster terminology)
- D - for double excitations (doubles)
- T - for triple excitations (triples)
- Q - for quadruple excitations (quadruples)
Thus, the operator in CCSDT has the form
Terms in round brackets indicate that these terms are calculated based on perturbation theory. For example, a CCSD(T) approach simply means:
- A coupled-cluster method
- It includes singles and doubles fully
- Triples are calculated non-iteratively.
Read more about this topic: Coupled Cluster
Famous quotes containing the words types of, types and/or methods:
“Science is intimately integrated with the whole social structure and cultural tradition. They mutually support one other—only in certain types of society can science flourish, and conversely without a continuous and healthy development and application of science such a society cannot function properly.”
—Talcott Parsons (1902–1979)
“The rank and file have let their servants become their masters and dictators.... Provision should be made in all union constitutions for the recall of leaders. Big salaries should not be paid. Career hunters should be driven out, as well as leaders who use labor for political ends. These types are menaces to the advancement of labor.”
—Mother Jones (1830–1930)
“I conceive that the leading characteristic of the nineteenth century has been the rapid growth of the scientific spirit, the consequent application of scientific methods of investigation to all the problems with which the human mind is occupied, and the correlative rejection of traditional beliefs which have proved their incompetence to bear such investigation.”
—Thomas Henry Huxley (1825–95)