Zhitova, E.S.; Sheveleva, R.M.; Zolotarev, A.A.; Krivovichev, S.V. The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide. Crystals2023, 13, 839.
Zhitova, E.S.; Sheveleva, R.M.; Zolotarev, A.A.; Krivovichev, S.V. The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide. Crystals 2023, 13, 839.
Zhitova, E.S.; Sheveleva, R.M.; Zolotarev, A.A.; Krivovichev, S.V. The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide. Crystals2023, 13, 839.
Zhitova, E.S.; Sheveleva, R.M.; Zolotarev, A.A.; Krivovichev, S.V. The Crystal Structure of Mg–Al–CO3 Layered Double Hydroxide. Crystals 2023, 13, 839.
Abstract
The crystal structure of quintinite, Mg4Al2(OH)12(CO3)·3H2O, from Jacupiranga alkaline complex (Cajati, São Paulo, Brazil) has been refined for two samples (91002 and C7029) using single-crystal X-ray diffraction data. The mineral crystallizes in the P-3c1 space group, a = 5.246/5.298, c = 15.110/15.199 Å for the samples 91002/C7029. The crystal structure consists of octahedral sheets with Mg and Al ordering according to the 3 × 3 superstructure. The Mg and Al atoms are coordinated by six hydroxylated oxygen atoms each with the average <Mg–O> and <Al–O> bond distances being in the ranges 2.022–2.053 Å and 1.974–1.978 Å, respectively. The interlayer structures are identical (in contradiction to the previous assumptions) and compose from disordered (CO3)2- groups and (H2O)0 molecules. The samples from Jacupiranga can be identified as quintinite-2T that is the second find of the polytype after the Kovdor alkaline complex (Kola peninsula, Russia). The powder X-ray diffraction pattern of quintinite-2T contains weak superstructure reflection at 4.57 Å (010) indicative of Mg and Al ordering. An important crystal-chemical criterion of quintinite is the interlayer distance (d00n-value) of ~ 7.56 Å, which is steady for natural specimens from various findings worldwide.
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