Chalcogenide density

Coleman, R. V., Giambattista, B., Hansma, P. K., Johnson, A., McNairy, W. W., and Slough, C. G. (1988). Scanning tunneling microscopy of charge-density waves in transition metal chalcogenides. Adv. Phys. 37, 559-644. 

In the cellular multiple scattering model , finite clusters of atoms are subjected to condensed matter boundary conditions in such a manner that a continuous spectrum is allowed. They are therefore not molecular calculations. An X type of exchange was used to create a local potential and different potentials for up and down spin-states could be constructed. For uranium pnictides and chalcogenides compounds the clusters were of 8 atoms (4 metal, 4 non-metal). The local density of states was calculated directly from the imaginary part of the Green function. The major features of the results are ... 

For the ion-by-ion reaction, nucleation is generally slower and the density of nuclei smaller. Additionally, growth occurs (ideally) only at a solid surface therefore nucleation is confined to two dimensions, in contrast to three dimensions for the cluster mechanism. The crystal growth may terminate when adjacent crystals touch each other or by some other termination mechanism, e.g., adsorption of a surface-active species. These factors should be valid regardless of whether the mechanism proceeds via free chalcogenide ions or by a complex-decomposition mechanism. 

No systematic study has been made to complete the list of substances given below. The reader is invited to look for further examples. The chalcogenide halides are formed by reaction of mixtures of the respective elements or binary components, or both, in the appropriate hydrogen halide acid under hydrothermal conditions. Temperatures are in the range of 500-100°C. The densities of the fluid are at least 55% of room-temperature values the corresponding pressures are not known in most cases. 

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