Plot of the a parameter against x for a range of Co–Al LDH phases reported in the literature. The data involve a variety of interlayer anions, which are represented by different symbols (that are identified in the figure legend). The full line is the result of the linear regression analysis of the data. The filled diamond represents the β polymorph of Co(OH)2 (Pertlik, 1999). The dashed line represents the values of a calculated from theory [using equation (1)]; the open diamond can be taken to represent a theoretical α form of Co hydroxide [Co(OH)2·H2O]. The data are from: Gabrovska et al. (2011), Géraud et al. (2008), Herrero et al. (2007), Intissar et al. (2003), Johnsen et al. (2010), Johnsen & Norby (2008), Johnson & Glasser (2003), Kannan et al. (1995), Kannan & Swamy (1999), Leroux, Moujahid et al. (2001), Liu et al. (2006), Luo & Dahn (2009), Pérez-Ramírez et al. (2001), Radha et al. (2007b), Ribet et al. (1999), Rives et al. (2003), Sato et al. (1988), Vieira et al. (2009).