Molecular electrostatic potential (MEP) and pattern recognition (PR) were used to draw potentially active pentamidine derivatives against Trypanosome brucei rhodesiense (T. b. rhodesiense). PR models: Principal Component Analysis, PCA model; Hierarchical Cluster Analysis, HCA model; K-Nearest Neighbor, KNN model; Soft Independent Modeling of Class Analogy, SIMCA model; and Stepwise Discriminant Analysis, SDA model, were built by reducing the dimensionality of a data matrix to twenty-eight pentamidine derivatives and allowed the compounds to be classified into two classes: more active and less active, according to their degrees of activity against T. b. rhodesiense. The study outlined that the properties HOMO (highest occupied molecular orbital) energy, VOL (molecular volume), and ASA_P (water accessible surface area of all polar (½qi½³0. 2) atoms) are the most relevant for the construction of the models. The key structural features required for biological activity investigated through MEP were used as guidelines in the design of thirteen new compounds, which were evaluated by PR models as more active or less active against T. b. rhodesiense. The application of PR models indicated nine promising compounds (29, 30, 31, 32, 33, 36, 37, 39, and 40) for synthesis and biological assays.

Douglas-Koll-Hess (DKH) second-order relativistic scalar approach was used to investigate piezoeletricity in gadolinium ferrite (GdFeO3). To adequately represent the polyatomic environment studied -(24s13p), ( 29s17p12d) and (32s22p16d10f)-basis sets were built for the atoms O ( 3 P), Fe ( 5 D), and Gd ( 9 D), then contracted to [4s2p], [12s6p5d], and [19s12p8d4f], respectively. The qualifying of the contracted basis sets for GdFeO3 crystal studies was conducted in three moments, namely: quality evaluation in molecular calculations, made in 1 FeO 1+ and 1 GdO 1+ molecular fragments; the choice of polarization function used in the [4s2p] basis set for O ( 3 P) atom; the choice of diffuse functions used in the [12s6p5d] and [19s12p8d4f] basis sets for Fe ( 5 D) and Gd ( 9 D) atoms, respectively. The qualified contracted basis sets gave rise to the molecular [4s2p1d]/[13s7p6]/[20s13p9d5f] basis set which was then used to describe geometric parameters of the GdFeO3 crystal. The good performance of the [4s2p1d]/[13s7p6d]/[20s13p9d5f] basis set in describing the geometry of the material of interest led to calculations of the material properties: total relativistic energy, dipole moment and total atomic charge. The analysis of the results for these properties showed that the possible piezoelectricity in GdFeO3 can be caused by electrostatic interactions of its atoms.