Professor at the Faculty of Sciences in Nancy (France), Niels Hansen passed away at the age of fifty-seven following a long period of illness.
After brilliant studies at the University of Aarhus, in Denmark, he prepared his doctorate in physical sciences at the University of New York in Buffalo under the supervision of Professor P. Coppens, a world-reputed crystallographer. In his thesis, he put forward a model to describe the electron density in solids, the importance of which is such that his name is now associated with it. Thirty years later, the Hansen-Coppens model is still the model most used by researchers in crystallography to describe the chemical bonding and the physical properties of materials related to the electron density. Understanding the behaviour of electrons in solids continued to be his main theme of research in the Hans Meitner Institute in Berlin, then in Nancy where he became Professor in 1983, in the Laboratory of Crystallography and Modelling of Mineral and Biological Materials.
His recent works, subsidised by the French National Research Agency, concern the comprehension of the piezoelectric effect which involves generating an electric field in a material such as quartz when submitted to pressure. This effect has a large number of applications in everyday life, from gas igniters to cell phones sensors and injectors. Understanding this phenomenon at the atomic level is a very important for the conception of higher performance materials.
A brilliant researcher of international status, while at the same time extremely discrete and kind, Professor Hansen was always at the disposition of PhD students and other researchers within the laboratory. He remained courageous throughout his illness, was a great contributor to the development of our laboratory and his absence will be greatly feltClaude Lecomte