Car-Parrinello, the LAPW Method and Large Systems

The development of the Car-Parrinello (CP) technique and its application to planewave based calculations resulted in a quantum increase in the size and complexity of the problems that can be treated within a fully ab initio LDA framework. This and related techniques combined with ultrasoft pseudopotentials make detailed structural investigations for unit cells of several hundred atoms quite feasible (Stich et al., 1992, Brommer et al., 1992). However, besides the general observations of Car and Parrinello, there are several special features of planewaves that are exploited, and these are crucial in making the CP method as efficient as it is (see Chapter 3). These are difficult to generalize to non-planewave basis sets, and because of this CP-like algorithms have yet to have a large impact with non-planewave basis methods.