Journal of

GEOsciences

  (Formerly Journal of the Czech Geological Society)

Original Paper

Sergey V. Krivovichev

Hydrogen bonding and structural complexity of the Cu₃(AsO₄)(OH)₃ polymorphs (clinoclase, gilmarite): a theoretical study

Journal of Geosciences, volume 62 (2017), issue 2, 79 - 85

DOI: http://doi.org/10.3190/jgeosci.231

Density functional theory (DFT) is used to determine positions of H atoms and to investigate hydrogen bonding in the crystal structures of two polymorphs of Cu₃(AsO₄)(OH)₃: clinoclase and gilmarite. Hydrogen bonds in clinoclase involve interactions between hydroxyl groups and O atoms of arsenate tetrahedra, whereas the crystal structure of gilmarite features OH^…OH bonding, which is rather uncommon in copper hydroxy-oxysalts. Information-based parameters of structural complexity for clinoclase and gilmarite show that the former is more complex (I_G,total = 213.212 bits/cell) than the latter (I_G,total = 53.303 bits/cell), which indirectly points out that gilmarite is metastable. This suggestion is supported by the lower density of gilmarite (4.264 g/cm³) compared to that of clinoclase (4.397 g/cm³). The hypothesis of metastable character of gilmarite is in agreement with the Goldsmith’s simplexity principle and the Ostwald-Volmer rule.