Self-consistent held methods

A number of types of calculations begin with a HF calculation and then correct for correlation. Some of these methods are Moller-Plesset perturbation theory (MPn, where n is the order of correction), the generalized valence bond (GVB) method, multi-conhgurational self-consistent held (MCSCF), conhgu-ration interaction (Cl), and coupled cluster theory (CC). As a group, these methods are referred to as correlated calculations. 

An MCSCF calculation in which all combinations of the active space orbitals are included is called a complete active space self-consistent held (CASSCF) calculation. This type of calculation is popular because it gives the maximum correlation in the valence region. The smallest MCSCF calculations are two-conhguration SCF (TCSCF) calculations. The generalized valence bond (GVB) method is a small MCSCF including a pair of orbitals for each molecular bond. 

In this contribution, we revisit the so-called Fenske-HaH molecular orbital (MO) method, an approximate self-consistent-held (SCF) ab initio method that contains no empirical parameters, which began almost 40 years ago in the research group of Richard... 

Other known methods that have been used in the study of lanthanides include the OP scheme, the LDA + U approach, where U is the on-site Hubbard repulsion, and the DMFT, being the most recent and also the most advanced development. In particular, when combined with LDA + U, the so-called LDA - - DMFT scheme, it has been rather successful for many complex systems. We note here that both DMFT and LDA + U focus mostly on spectroscopies and excited states (quasiparticles), expressed via the spectral DOS. In a recent review article (Held, 2007), the application of the LDA + DMFT to volume collapse in Ce was discussed. Finally, the GW approximation and method, based on an electron self-energy obtained by calculating the lowest order diagram in the dynamically screened Coulomb interaction, aims mainly at an improved description of excitations, and its most successful applications have been for weakly correlated systems. However, recently, there have been applications of the quasi-particle self-consistent GW method to localized 4f systems (Chantis et al., 2007). 

The self-consistent reaction held (SCRF) method is an adaptation of the Poisson method for ah initio calculations. There are quite a number of variations on this method. One point of difference is the shape of the solvent cavity. Various models use spherical cavities, spheres for each atom, or an isosurface... 

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