Surface physics has experienced in the last two decades an explosive expansion caused by the development and/or substantial improvement of surface sensitive techniques and UHV apparatuses. It has grown into a mature field of research, with data of the highest accuracy and reproducibility. Surface physics is of great importance for technological applications like field effect devices, molecular beam epitaxy, chemisorption and catalysis, corrosion, surface hardening etc. The present volume III/24 is restricted to the so called 'clean' surfaces, i.e. to surfaces atomically clean and well characterized, leaving the more complex field of the contaminated surfaces and overlayers to a later occasion. Due to the large amount of data this volume is divided into four subvolumes: III/24a, b, c, d (see below). Each chapter consists of an introduction giving a brief presentation of the subject and a data section in form of tables, figures, and pictures. There is a general index in which all data are ordered alphabetically according to the material and to the surface is given at the end of subvolume III/24d.