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The influence of quantum effects on the critical properties of an n-component vector model for structural phase transitions is explored, It is shown for n = 1, 2, and 00 that these effects can suppress the occurrence of a phase transition for all dimensions d. This turns out to be of particular relevance for systems where the classical transition temperature almost vanishes (T, = 0 represents the displacive limit). We also discuss the critical properties at this limit for n = cc and show that the critical exponents change discontinously,

The atomic force microscope (AFM) is a promising new method for studying the surface structure of both conductors and insulators. In mapping a graphite surface with an insulating stylus, we have achieved a resolution better than 2.5 fi.

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