Configuration interaction effective core potential

Configuration Interaction by Perturbation with Multiconfigurational Zero-Order Wave Function Selected by Iterative Process Configuration Interaction with Singles and Doubles Density Functional Theory Effective Core Potential Generalized Gradient Approximation Hartree-Fock... 

Comparison of Spin—Orbit Configuration Interaction Methods Employing Relativistic Effective Core Potentials for the Calculation of Zero-Field Splittings of Heavy Atoms with a 2P° Ground State. 

Fig. 4. All-electron, effective potential, and average relativistic effective core potential configuration-interaction potential-energy curves of Xe2 and Xe2+. Dashed curves are from allelectron calculations and AREP curves are less repulsive than EP.

Our above-mentioned conclusions are contrary to the results reported from previous less rigorous calculations e.g.. Hay et al. (11) concluded from an effective core potential (ECP) calculation using an approximate treatment of relativity that the 5d core does not appear to play a dominant role in the chemical bond in AuH this conclusion is incorrect in view of our result that 5d electrons cannot be left in the core in AuH. Our extended basis set (EBS), DF SCF calculation predicts a value of 1.682 eV for the D of AuH and our relativistic configuration interaction calculation with the... 

By ab initio we refer to quantum chemical methods in which all the integrals of the theory, be it variational or perturbative, are exactly evaluated. The level of theory then refers to the type of theory employed. Common levels of theory would include Hartree-Fock, or molecular orbital theory, configuration interaction (Cl) theory, perturbation theory (PT), coupled-cluster theory (CC, or coupled-perturbed many-electron theory, CPMET), etc. - We will use the word model to designate approximations to the Hamiltonian. For example, the zero differential overlap models can be applied at any level of theory. The distinction between semiempirical and ab initio quantum chemistry is often not clean. Basis sets, for example, are empirical in nature, as are effective core potentials. The search for basis set parameters is not usually considered to render a model empirical, whereas the search for parameters in effective core potentials is so considered. 

Relativistic and electron correlation effects play an important role in the electronic structure of molecules containing heavy elements (main group elements, transition metals, lanthanide and actinide complexes). It is therefore mandatory to account for them in quantum mechanical methods used in theoretical chemistry, when investigating for instance the properties of heavy atoms and molecules in their excited electronic states. In this chapter we introduce the present state-of-the-art ab initio spin-orbit configuration interaction methods for relativistic electronic structure calculations. These include the various types of relativistic effective core potentials in the scalar relativistic approximation, and several methods to treat electron correlation effects and spin-orbit coupling. We discuss a selection of recent applications on the spectroscopy of gas-phase molecules and on embedded molecules in a crystal enviromnent to outline the degree of maturity of quantum chemistry methods. This also illustrates the necessity for a strong interplay between theory and experiment. 

Abstract An implementation of a massively parallel spin-orbit configuration interaction (PSOCI) method is described. This is an extension of a conventional Cl method that explicitly includes one-electron spin-orbit operators and certain scalar relativistic effects extracted from relativistic effective core potentials. The performance of the PSOCI code is analyzed on several large-scale computing platforms. 

AIMD = ab initio molecular dynamics B-LYP = Becke-Lee-Yang-Parr CCSD = coupled cluster single double excitations CVC = core-valence correlation ECP = effective core potential DF = density functional GDA = gradient corrected density approximation MCLR = multiconfigurational linear response MP2 = M0ller-Plesset second-order (MRD)CI = multi-reference double-excitation configuration interaction RPA = random phase approximation TD-MCSCF = time-dependent multiconfigurational self-consistent field TD-SCF = time-dependent self-consistent field. 

The calculations were performed with several different levels of correlation treatment Hartree-Fock (HF), configuration interaction with single and double excitations (SDCI), Multiconfiguration self consistent field (CAS), and multireference configuration interaction (MRCI). Relativistic efferts were accounted for using either the Douglas-Kroll method or a relativistic effective core potential approach (RECP). 

V. Bonacic-Koutecky, L. Cespiva, P. Fantucci, J. Pittner, and J. Koutecky, Effective Core Potential-Configuration Interaction Study of Electronic Structure and Geometry of Small Anionic Agn Clusters Predictions and Interpretation of Photodetachment Spectra , J. Chem. Phys. 100, 490 (1994). 

Configuration Interaction Density Functional Theory (DFT), Hartree-Fock (HF), and the Self-consistent Field Density Functional Theory Applications to Transition Metal Problems Metal Complexes Relativistic Effective Core Potential Techniques for Molecules Containing Very Heavy Atoms Relativistic Effects of the Superheavy Elements Relativistic Theory and Applications Transition Metal Chemistry Transition Metals Applications. 

CSF = configurational spin functions GUGA = graphical unitary group approach MRSDCl = multireference singles and doubles configuration interaction RCl = relativistic Cl RECP = relativistic effective core potential. 

Basis Sets Correlation Consistent Sets Benchmark Studies on Small Molecules Complete Active Space Self-consistent Field (CASSCF) Second-order Perturbation Theory (CASPT2) Configuration Interaction Configuration Interaction PCI-X and Applications Core-Valence Correlation Effects Coupled-cbister Theory Density Functional Applications Density Functional Theory (DFT), Har-tree-Fock (HF), and the Self-consistent Field Density Functional Theory Applications to Transition Metal Problems Electronic Structure of Meted and Mixed Nonstoi-chiometric Clusters G2 Theory Gradient Theory Heats of Formation Hybrid Methods Metal Complexes Relativistic Effective Core Potential Techniques for Molecules Containing Very Heavy Atoms Relativistic Theory and Applications Semiempiriced Methetds Transition Metals Surface Chemi-ced Bond Transition Meted Chemistry. 

The drive toward reliable quantum mechanical predictions for large molecular systems is well represented in ECC articles by George Bacskay Solvation Modeling), Krishnan Balasub-ramanian Relativistic Effective Core Potential Techniques for Molecules Containing Very Heavy Atoms), Margareta Blomberg Configuration Interaction PCI-X and Applications), and Keiji Morokuma Hybrid Methods). 

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