Thermodinamic Interpretaion of the Morphology Individuality of Natural and Synthesized Apatite Single Crystals

Abstract

Specific surface free energy (SSFE) of natural calcium fluorapatite from the same mother rock and synthesized barium chlorapatite from the same lot was determined using contact angle of water and formamide droplets, compared with grown length of crystal face (h). The experimentally obtained SSFEs have different values even for the same index faces of the different crystals. The SSFEs also have wide distribution for each face of crystals. Observed SSFE is considered to be not only the SSFE of ideally flat terrace face, but also includes the contribution of strep free energy. Though the crystals we experimentally obtained were growth form, the relationship between SSFE and h was almost proportional, which looks like satisfying Wulff's relationship qualitatively. The slope of SSFE versus h line shows the driving force of crystal growth, and the line for larger crystal has less steep slope. The driving force of crystal growth for larger crystal is smaller, which also means that the chemical potential is larger for larger crystal. The individuality of crystals for the same lot can be explained by the difference of the chemical potential of each crystal.

Dispersion and Polar Component of Specific Surface Free Energy of NaCl(100), KCl(100), and KBr(100) Single Crystal Surfaces

“…Calculated SSFE of NaCl, KCl, and KBr and dispersion and polar components of them are summarized in Table 2. In our previous research, we did not discuss the dispersion and polar component separately, but we discussed summed SSFE only [7]- [9]. γ is very small.…”

“…We adopted this established experimental method to determine the SSFE of some inorganic crystals, ruby [7], quartz [8], and apatite [9], using contact angle of liquid droplet. In this work, we are studying alkali halide crystals, and discussing the detailed meaning of SSFE of crystal, especially dispersion and polar components of SSFE.…”