Struct Bond (2012) 149: 95–130 DOI: 10.1007/978-3-642-32753-7_3 # Springer-Verlag Berlin Heidelberg 2012 Applying Conventional Ab Initio and Density Functional Theory Approaches to Electric Property Calculations. Quantitative Aspects and Perspectives George Maroulis Abstract We have examined the predictive capability of density functional theory methods in calculations of electric polarizability and hyperpolarizability. We have focused on test cases belonging to three high-priority classes of molecular systems: “soft” metal clusters, novel types of compounds, and weakly bonded molecules. The performance of theoretical methods over arbitrary collections of molecular properties can be analyzed and classified by the introduction of a new methodology based on graph theoretic considerations and pattern recognition techniques. Keywords Ab initio  Density functional theory  Electric (hyper)polarizability Contents 1 Introduction .................................................................................. 96 2 Theoretical Considerations .................................................................. 97 2.1 Electric Properties of Atoms, Molecules, and Clusters. Basic Theory and Computational Aspects ............................................................... 97 2.2 Interaction-Induced Electric Properties .............................................. 99 2.3 Proximity, Similarity, and Order in Spaces of Theoretical Descriptions ........... 100 3 Results ....................................................................................... 102 3.1 Sodium Tetramer, a Very Soft Molecule ............................................. 102 3.2 New Classes of Molecules, the Case of HXeI ....................................... 111 3.3 Interaction-Induced Polarizability and Hyperpolarizability of Two Water Molecules .............................................................................. 119 4 Final Remarks and Conclusions ............................................................ 125 References ....................................................................................... 126 G. Maroulis (*) Department of Chemistry, University of Patras, Patras 26500, Greece e-mail: maroulis@upatras.gr