Commensurate-incommensurate transitions of physisorbed films on anisotropic substrates

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Abstract
Commensurate-incommensurate transitions in dimension D = 2 have previously been investigated by Pokrovskii and Talapov, Schulz, and Okwamoto (PTSO). Some of their results are reproduced here by means of a simple dimensional argument. In addition, new results are obtained in the low temperature region. The temperature dependence of relevant parameters is specified, and different behaviours of various systems are pointed out. The range of validity of the PTSO square root behaviour is calculated at low temperature by an exact method. This range of validity is found to be very narrow. An improved formula, valid in a broader range, is proposed. On metal surfaces the PTSO mechanism is probably dominated by electric dipole interactions. Theoretical results are compared with recent experiments. The temperature variation of the transition chemical potential μ c(T) is qualitatively discussed in the experimentally available temperature region