Preface: phys. stat. sol. (a) 202/12
Authors: Neumann Wolfgang , Stutzmann Martin , Hildebrandt Stefan 
Published: September 2005

The present special issue contains a collection of Original Papers dedicated to Professor Johannes Heydenreich on the occasion of his 75th birthday.

Johannes Heydenreich, born on 20 June 1930 in Plauen/Vogtland near Dresden, studied physics at the Pädagogische Hochschule Potsdam, where he obtained his first academic degree “Dipl. Phys.” in 1958. He received his doctoral degree at the Martin Luther University in Halle in 1961 and the Habilitation degree in 1969. Already during his studies in Potsdam, he showed an interest in electron microscopy due to the influence of his teacher and supervisor Prof. Picht, one of the pioneers in electron optics. His interests were strengthened when Johannes Heydenreich did the experimental work for his Diploma degree at the Institute for Experimental Physics of the University of Halle, where he met Prof. Heinz Bethge for the first time. This was the beginning of a fruitful and longstanding collaboration. In 1962 Johannes Heydenreich joined the team of the later Institute for Solid State Physics and Electron Microscopy of the Academy of Sciences of the GDR, in Halle, for which the basis was laid by Prof. Bethge in 1960.

Heydenreich has been working as Assistant Director for many years and played a decisive role in introducing and organising the various techniques of electron microscopy in the institute.

The research activities of Prof. Heydenreich covered a broad spectrum over the years. At the beginning of his career he made significant contributions in the field of electron mirror microscopy. After that, his main interests were focused on transmission electron microscopy, ranging from diffraction contrast analysis of crystal defects to high‐resolution electron microscopy and image processing. His favourite field was studies of defect‐induced phenomena in advanced materials. The so‐called Bethge–Heydenreich, the book “Electron Microscopy in Solid State Physics”, published at first in a German edition in 1982 and later in a revised English edition by Elsevier in 1987, provides an excellent overview both of Heydenreich's work and of the spectrum of the Institute of Solid State Physics and Electron Micros‐copy in Halle.

The international reputation of this institute was the basis for the transformation of it, after the re‐unification of Germany, into the Max Planck Institute of Microstructure Physics, the first institute of the Max Planck Society in the Eastern part of Germany. From the beginning, Prof. Heydenreich was on the Board of Directors and served as the Executive Director from 1993 until his retirement in 1995.

During this year, the International Centre of Advanced Materials and Electron Microscopy celebrates its 30th anniversary. The Centre was founded in Halle in 1975 as a Centre of Electron Microscopy for the Eastern countries.

A remarkable and time‐consuming part of Heydenreich's work was associated with this centre. Young scientists from Eastern Europe were trained in the theoretical and practical aspects of electron microscopy during the annual spring and autumn meetings. All in all, Johannes Heydenreich conducted 35 of these schools! From the beginning, he was a member of the Scientific Council of the Centre, and from 1985 until his retirement he was the Director of the Centre. Nowadays, the Centre acts as a real bridge between East and West largely due to the efforts of Johannes Heydenreich.

Furthermore, Johannes Heydenreich had been active as a leading member of various scientific boards for many years. He was a co‐editor of several journals covering electron microscopy, solid state physics and crystallography. As a member of the Executive Committee of the European Society for Elec‐tron Microscopy (CESEM) for many years, and as a member of the Executive board of the German Soci‐ety for Electron Microscopy, Johannes Heydenreich has invested a great deal of time and effort in the welfare of the scientific community.

Over the course of nearly three decades, Johannes Heydenreich worked as a Professor at the Universities of Halle and Leipzig. Generations of students have admired his excellent lectures with clear repre‐sentation and rigorous scholarship.

The scientific work of Johannes Heydenreich was honoured by his election to the Academy of Natural Scientists Leopoldina where he worked as a Secretary of Natural Science for many years. The Technical University of Chemnitz conferred an honory doctors degree on Prof. Heydenreich in recognition of his scientific work. The German Society for Electron Microscopy awarded him Honorary Membership.

Wolfgang Neumann especially acknowledges with gratitude the time of inspiring collaboration in Halle.

All his friends, colleagues, and students wish him many further years of good health. The Editors of physica status solidi join these wishes and add their gratefulness for his long‐standing and continuous engagement as a member of the Advisory and Editorial Board of physica status solidi (a).