New computer tools of the Bilbao crystallographic server for materials structural analysis

Resumen

The objective of this Thesis is the development of new databases and tools related to the application ofsymmetry methods in the analysis of crystalline structures and their physical properties. The computerprograms are implemented in the Bilbao Crystallographic Server (http://www.cryst.ehu.es), a freelyaccessible web server whose relevance in the field of crystallography is demonstrated by the growingnumber of users, and by the number of external links from institutions and universities, as well as by thepopularity ratings of the web. The new computational tools are related to problems of structural chemistry,solid-state physics or representation theory of crystallographic groups. There are modules for comparison ofcrystal structures and evaluation of their similarity, identification of different phases and structure types aswell as searching for compatible pseudo-symmetry transformations, which is very important for the study andclassification of materials with complex structures and/or subtle structural deviations from high-symmetry,aristotype structures. The user-friendly design of the programs of the server and in particular of the new setof programs for group-theoretical analysis of infrared, Raman and hyper-Raman scattering processes aim tobring the potential of group theory to those users who are not necessarily experts in the field but want to usesymmetry methods in their studies of materials.The efficiency and utility of the developed computer programs has been demonstrated by a number ofillustrative examples. An important part of this Thesis is related to specific practical applications of the newprograms implemented in the Bilbao Crystallographic Server, among which one should mention theclassification of isopointal structures into isoconfigurational structure types and the selection-rulescalculations for resonance Raman scattering processes and their application in the group-theoretical analysisof resonance Raman spectra of relaxor ferroelectrics.