Relativistic LCAO Methods for Periodic Systems

The influence of relativistic effects on the structural and electronic properties of the crystals with heavy elements is well known [541]. 

The four-component DHF LCAO equations for ID-, 2D- and 3D-periodic systems were at first presented by Ladik [547]. The resulting somewhat compUcated generaUzed matrix eigenvalue equation for solids is described (for details we refer the reader to [547]). It was also shown for ID and 2D systems how MP2 methods could be applied iu their relativistic form. With the help of these, on the one hand, the total energy per unit cell (including correlation effects) can be computed. On the other hand, the relativistic band structure can also be corrected for correlation. Note that the symmetry of crystaUine orbitals changes, compared with the nonrelativistic case, as the symmetry of the DHF Hamiltonian is described by double space groups. Finally, 

Each transformation C/ is chosen in such a way that the offdiagonal blocks of the Dirac Hamiltonian are zero to a given order in the potential. The decoupled, block- 

The large-component block, is the two-component effective Hamiltonian to 

The reoptimized nncontracted correlation corrected basis sets were used. The diffuse exponents ( 0.04) in the basis set for Ag were discarded. The results given in Table 8.6 demonstrate the inflnence of scalar-relativistic effects in the AgX crystals 

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