Density Functional Theory Simulation of the Hydrogen Bonding System in Sampleite

The article presents a crystal-chemical description of the second occurrence of the P2₁/n modification of sampleite, NaCaCu₅(PO₄)₄Cl·5H₂O, discovered at the Kester tin deposit. The formation of this mineral is genetically associated with low-temperature oxidation processes of primary copper, zinc, and tin sulfides, as well as with the formation of later Cu- and Zn-phosphates such as batagayite, epifanovite, and sergeysmirnovite. The positions of hydrogen atoms in the structure of sampleite were calculated using the density functional theory method. To assess the reliability of the theoretical calculations, a comparison between the actual and theoretical IR spectra was conducted. Sampleite formed during the hydrothermal alteration stage of Sn, Cu, and Zn sulfide minerals and coexisted with epifanovite, NaCaCu₅(PO₄)₄[AsO₂(OH)₂]·7H₂O. Epifanovite is undoubtedly a later mineral but has a lower structural complexity (I_{G, total}) of 474.24 bits/cell, compared to sampleite, which has a complexity of 933.32 bits/cell.