This book contains the papers presented at the NATO Advanced Study Institute held at Ustaoset H¢yfjellshotel, near Geilo, Norway, 24th April - 1st May, 1973. The members of the Programme Committee were J. D. Axe Brookhaven National Laboratory, USA J. Feder University of Oslo, Norway T. Riste Institutt for Atomenergi, Norway (Chairman) The title of the institute, "Anharmonic Lattices, Structural Transi tions and Melting", gives an idea of the programme and of the content of this book. The first part is devoted to the so­ called "central mode" at 2nd order structural phase transitions, a phenomenon which was first reported in 1971 at a NATO Advanced Study Institute held at Geilo. (Several references to the pro­ ceedings of that institute, entitled "Structural Phase Transitions and Soft MOdes", are found in the present volume). From 2nd order transitions the emphasis of the programme moves gradually to 1st order transitions by covering such topics as order-disorder structural transitions in simple molecular crystals and tricritical phenomena. The last part is devoted to melting, including dis­ cussions on the dynamics of solids and liquids near their melting points. The lectures are divided almost equally between review talks and research reports dealing with subjects closely connected with the topics under review. With a few exceptions the lectures are printed in the sequence of presentation at the study institute. The total number of participants was limited to 71, their names are given at the end of the book.

Phase Transitions, Anharmonic Solids and Liquids.- Neutron Scattering Studies of Soft Mode Dynamics.- Slow Local Fluctuations near Tc in SrTio3 Studied by EPR.- Hydrodynamics near Phase Transitions of Second Order.- Review of Methods for Obtaining a Central Mode.- Nonlinear Fluctuations and the Central Mode.- Some Further Observations of Soft Phonon Line Shapes in KMnF3.- Critical Sound Velocity and Attenuation in KMnF3.- Raman Spectral Study of the Upper Phase Transition in KMnF3.- Soft Mode and Critical Opalescence in SrTio3.- Phonon Transport Theory and the Central Mode.- Phase Transitions in Solid CD4.- The Jahn-Teller Effect as a Mechanism for Structural Phase Transitions.- Soft Modes at First and Second Order Phase Transitions.- A Qualitative Picture of the Tricritical Point.- Tricritical Studies of ND4Cl.- Computer Simulation of a Discontinuous Phase Transition in the Two-Dimensional One-Spin-Flip Ising Model.- Continuous versus Discontinuous Phasetransitions.- Dynamics of Fluids Near the Critical Point: Light Scattering Investigations.- Neutron Scattering in Solid and Liquid H2.- Neutron Scattering by a Liquid Crystal at Temperatures Close to Its Melting Point.- X-Ray Studies of the Smectic Structure and the Solid-Smectic Transition.- High-Frequency Dynamics of Simple Solids and Liquids Near Their Melting Points.- Analysis of the Approach to the Convective Instability Point.- Melting: Theories and Recent Computer Simulations.- Volume Expansion, Thermal and Electrical Conductivities and Sound Velocities of Sodium at Temperatures Very Close to Its Melting Point.- List of Participants.