Journal of Mineralogical and Petrological Sciences
Online ISSN : 1349-3825
Print ISSN : 1345-6296
ISSN-L : 1345-6296
LETTERS
Hydrogen distribution in chondrodite: a first–principles calculation
Masami KANZAKI
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2016 Volume 111 Issue 6 Pages 425-430

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Abstract

In synthetic hydroxyl–chondrodite and hydroxyl–clinohumite, two hydrogen sites (H1 and H2) are known. However, hydrogen occupying only H1 site has been reported for natural F– and Ti–rich chondrodite and clinohumite. In order to understand hydrogen distribution in these sites, stability of hydrogens at these sites in chondrodite is studied by first–principles density functional theory calculation. For hydroxyl–chondrodite, lowest energy was found when both H1 and H2 sites are half occupied by hydrogens. In this configuration, strong H1–H1 repulsion is avoided, and nearly straight hydrogen bond of O–H1•••O–H2 is realized. When a half of OH is replaced with F or replaced with O2− in the case of Ti–containing systems, hydrogen occupying H1 site is always favored over hydrogen in H2 site so as to form nearly straight hydrogen bond of O–H1•••F (or O2−). Our calculations are fully consistent with the observed structures in both synthetic and natural chondrodite, and revealed that hydrogen distribution in humite group minerals is mostly governed by hydrogen bonding at H1 site.

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© 2016 Japan Association of Mineralogical Sciences
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