CISD configuration interaction singles and

Let s compare these CASSCF results with those for a method that is not size-consistent, Cl with no complete aspect. We ll use CISD (configuration interaction singles and doubles Section 5.4.3). Here are the results for CISD/6-31G ... 

CISD... Configuration Interaction. Single and Double Excitation. CCSD... Coupled Cluster. Single and Double Excitation. 

CISD Model. Configuration Interaction, Singles and Doubles. A limited Configuration Interaction scheme in which only single and... 

CISD. CISD (configuration interaction, single double) are LCAO expressions that treat configuration interactions by including one or two excited states. The designations CISDT and CISDTQ expand this to three and four excitations, respectively. 

Cl methods [21] add a certain number of excited Slater determinants, usually selected by the excitation type (e.g. single, double, triple excitations), which were initially not present in the CASSCF wave function, and treat them in a non-perturbative way. Inclusion of additional configurations allows for more degrees of freedom in the total wave function, thus improving its overall description. These methods are extremely costly and therefore, are only applicable to small systems. Among this class of methods, DDCI (difference-dedicated configuration interaction) [22] and CISD (single- and double excitations) [21] are the most popular. 

CISD configuration interaction with single and double excitations... 

CISD configuration interaction with singly and doubly excited determinants only DRE Dewar resonance energy... 

CISD Configuration interaction with singles and doubles... 

Zero-Order Wave Function Selected by Iterative Process CISD Configuration Interaction with Singles and Doubles... 

CISD Configuration Interaction using Single and Double excitations. 

As has been demonstrated by numerous studies, the accuracy of properties calculated using the GGA DFT methods is, in most cases, comparable to or better than those from ab initio MP2 (Mpller-Plesset second-order perturbation) or CISD (configuration interaction with single and double excitations) methods. In fact, the accuracy of the DFT results in some instances matches those obtained from the much more costly (but, in principle, more exact) CCSD(T) (coupled cluster singles and doubles with a perturbative inclusion of connected triple excitations) method (29) and the ab initio G1 procedure (30). 

CISD - Configuration Interaction including Single and Double excitations, HF - Haitree-Fock... 

LDA - Local Density Approximation, N-LDA - gradient corrected LDA, HF - Hartree-Fock, CISD - Configuration Interaction including Single and Double excitations, MP2(4) - second (fourth) order Moller-Plesset perturbation theory... 

The explicit time-dependent configuration interaction (TD-CI) method has been applied to calculate the linear and nonlinear electric responses of H2 and H2O molecules to external time-dependent perturbations. Three variants have been employed to solve the time-dependent Schrodinger equation, namely, the TD-CIS (inclusion of single excitations only), TD-CISD (inclusion of single and double excitations), and TD-CIS(D) (single excitations and a perturbative treatment of the double excitations) methods. The authors have stressed that one of the biggest advantages of this approach is its ability to tackle molecular responses to pulses with arbitrary time-dependence, even beyond perturbation theory. 

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