CC, coupled cluster

Cartesian coordinates system for locating points in space based on three coordinates, which are usually given the symbols x, y, z or i, j, k CBS (complete basis set) an ah initio method CC (coupled cluster) a correlated ah initio method CFF (consistent force field) a class of molecular mechanics force fields CFMM (continuous fast multipole method) a method for fast DFT calculations on large molecules... [Pg.361]

CC Coupled Cluster. A means of including dynamic electron correlation that includes higher-order excitations. [Pg.393]

The CC (Coupled-Cluster) method is an attempt to find such an expansion of the wave function in terms of the Slater determinants, which would preserve size consistency. In this method the wave function for the electronic ground state is obtained as a result of the operation of the wave operator exp(f) on the Hartree-Fock function (this ensures size consistency). The wave operator exp(f) contains the cluster operator T, which is defined as the sum of the operators for the /-tuple excitations, 7) up to a certain maximum I = /max- Each fi operator is the sum of the operators each responsible for a particular l-tuple excitation multiplied by its amplitude t. The aim of the CC method is to find the t values, since they determine the wave function and energy. The method generates non-linear... [Pg.562]

Figrire 8 An overview of quantum chemical methods for excited states. Bold-italic entries indicate methods that are currently applicable to large molecules. Important abbreviations used Cl (configuration Interaction), TD (time-dependent), CC (coupled-cluster), HF (Hartree-Fock), CAS (complete active space), RAS (restricted active space), MP (Moller-Plesset perturbation theory), S (singles excitation), SD (singles and doubles excitation), MR (multireference). Geometry optimizations of excited states for larger molecules are now possible with CIS, CASSCF, CC2, and TDDFT methods. [Pg.176]

CC Coupled-cluster theory, where the correlated wavefunction is created from Fg by acting on the latter with an exponential operator exp(T), which creates excited configurations. An infinite-order variant of (->) MBPT. Unlike (—>) MP2 or (- ) Cl, the solution of the CC equations requires an iterative procedure. [Pg.86]