 | Acta Crystallographica Section B Acta Crystallographica Section B STRUCTURAL SCIENCE, CRYSTAL ENGINEERING AND MATERIALS |
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![[Figure 24]](bk0150fig24mag.jpg)
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Figure 24
Hexamethylbenzene – plot of volume per molecule in the three phases. The regions of stability of the three polymorphs are shown. The crosses show measured values (XRD) for the hydrogenated compound (at 19 and 293 K from Santarsiero et al., 2005  ; at 20 K from Stride, 2005; at 123 K from Le Maguéres et al., 2001; at 428 K from Watanabe et al., 1949). The crossed squares show measured values for the deuterated compound (Stride, 2005). The Stride values are by neutron diffraction on polycrystalline samples except for the 20 K XRD value. The slopes of the V/T curves are taken as linear; we calculate from Stride's results that dV/dT (phase EI, d18) is 0.0253 Å3 K−1 and, for phase II (h18) 0.051 Å3 K−1 (from Le Maguéres et al., 2001 and Santarsiero et al., 2005). These values are in good agreement with those given by Santarsiero – 0.025 and 0.057 Å3 K−1, respectively. The volume change at the EI/EII transition is 0.4 A3 per molecule (from Table 2 of Stride, 2005), while that for the triclinic/orthorhombic transition was measured as 6.1 Å3 (Chihara & Seki, 1948). |
![[Figure 24]](bk0150fig24.jpg)
| STRUCTURAL SCIENCE CRYSTAL ENGINEERING MATERIALS |
ISSN: 2052-5206
