Herringbone lattice constants

Figure 33. Herringbone orientational correlation functions F (3.15) in the inset and the logarithmic derivatives 62 In (3.18) as a function of distance I in units of the lattice constant a - 4.26 A in the disordered phase of the anisotropic-planar-rotor model (2.5) from Monte Carlo simulations at 7" = 25.5 K and a linear system size of L = 180. The different symbols distinguish the three symmetty axes a, and the dashed line marks the plateau 2/. In the inset all three F fall on top of each other and the different symbols denote here the two oscillating parts of the antiferromagnetic-like ordering pattern. (Adapted from Fig. 1 of Ref. 273.)...

Uniaxially compressed phases and the commensurate reference stmcture were furthermore examined [342] by molecular dynamics simulations along the lines of the work reported in Refs. 232 and 340 (see Section III.D.l), except for small alterations in the potential models. The 96 molecules were put into a rectangular cell which was uniaxially compressed by 5 % perpendicular to a glide line of the herringbone sublattice stmcture that is, the center-of-mass lattice is contracted toward the glide line this compression allows the same periodic boundary conditions to be effective for both adsorbate and graphite lattices. It should be noted, however, that even this does not ensure a simulation of the tme equilibrium situation because every solid accommodates even in equilibrium a certain number of vacancies and interstitials. In simulations with a constant number of particles the net number of such defects is acmally constrained to some constant value, which is not necessarily the correct equilibrium value [338, 339]. Two temperatures well below and above the orientational disordering transition at 15 K and... 

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