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The Ti and Zr K‐edge X‐ray absorption near edge structure (XANES) spectra of ATiO3 (A = Sr, Ba, and Pb) and PbZrO3 perovskite‐type compounds have been measured in the temperature range 20–900 K. Quantitative comparison is performed in a wide temperature range to clarify how the intensities of the pre‐edge peaks and shoulders change with temperature. In the ferro‐ and antiferroelectric tetragonal phases, the intensities of some of the peaks and shoulders decrease with increasing temperature and the peak‐top energies shift to the higher energy side. The shift can be explained by the position and decrease (increase for SrTiO3) of the D2 peak in the difference spectra. The peak‐top position of the pre‐edge peak in XANES does not always represent the true energy for independent transition to an orbital because several orbitals with similar energies overlap. The tetragonal SrTiO3 phase shows the same behavior as ferroelectric P4mm tetragonal BaTiO3 and PbTiO3 perovskite. The temperature dependence of the shoulder is also an important index. The presence of a phase with local polar tetragonal strain is important in materials and the Earth's constituent solid solutions. The existence of ferro‐ and antiferroelectricity can be determined by temperature‐dependent XANES measurements.

The structure refinement and XANES study of two gold–silver–tellurides [Au1+x Ag x Te2, krennerite (x = 0.11–0.13) and sylvanite (x = 0.29–0.31)] are presented and the structures are compared with the prototype structure of calaverite (x = 0.08–0.10). Whereas the latter is well known for being incommensurately modulated at ambient conditions, neither krennerite nor sylvanite present any modulation. This is attributed to the presence of relatively strong Te—Te bonds (bond distances < 2.9 Å) in the two minerals, which are absent in calaverite (bond distances > 3.2 Å). In both tellurides, trivalent gold occurs in slightly distorted square planar coordination, whereas monovalent gold, partly substituted by monovalent silver, presents a 2+2+2 coordination, corresponding to distorted rhombic bipyramids. The differentiation between bonding and non-bonding contacts is obtained by computation of the Effective Coordination Number (ECoN). The CHARge DIstribution (CHARDI) analysis is satisfactory for both tellurides but suggests that the Te—Te bond in the [Te3]2− anion is not entirely homopolar. Both tellurides can therefore be described as Madelung-type compounds, despite the presence of Te–Te in both structures.

Single crystals of Ni3Se2 (trinickel diselenide) and NiSe (nickel selenide) with stoichiometric chemical compositions were grown in evacuated silica-glass tubes. The chemical compositions of the single crystals of Ni3Se2 and NiSe were determined by scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDS). The crystal structures of Ni3Se2 [rhombohedral, space group R32, a = 6.02813 (13), c = 7.24883 (16) Å, Z = 3] and NiSe [hexagonal, space group P63/mmc, a = 3.66147 (10), c = 5.35766 (16) Å, Z = 2] were analyzed by single-crystal X-ray diffraction and refined to yield R values of 0.020 and 0.018 for 117 and 85 unique reflections, respectively, with F o > 4σ(F o). R32 is a Sohncke type of space group where enantiomeric structures can exist; the single-domain structure obtained by the refinement was confirmed to be correct by a Flack parameter of −0.05 (2). The existence of Ni—Ni bonds was confirmed in both compounds, in addition to the Ni—Se bonds. The value of the atomic displacement parameter (mean-square displacement) of each atom in NiSe was larger than that in Ni3Se2. The larger amplitude of the atoms in NiSe corresponds to longer Ni—Se and Ni—Ni bond lengths in NiSe than in Ni3Se2. The Debye temperatures, θD, estimated from observed mean-square displacements for Ni and Se in Ni3Se2, were 322 and 298 K, respectively, while those for Ni and Se in NiSe were 246 and 241 K, respectively. The existence of large cavities in the structure and the weak bonding force are likely responsible for the brittle and soft nature of the NiSe crystal.

The crystal structures of skorpionite from the Skorpion zinc deposit in Namibia [Ca 3 Zn 2 (PO 4) 2 CO 3 (OH) 2 •H 2 O; monoclinic; a = 19.0715(8), b = 9.3321(3), c = 6.5338(3) Å, β = 92.6773(12)°; space group C 2/c] and [a = 19.0570(14), b = 9.3346(5), c = 6.5322(4) Å, β = 92.752(2)°; space group Cc] are analyzed using single-crystal X-ray diffraction and refined to yield R values of 0.0253 and 0.0272 for 1576 and 2446 unique reflections with F o > 4σ(F o), respectively. Hydrogen atoms in the structure determined by the difference Fourier method. Although two space groups, C 2/c and Cc, are possible, the Cc space group without center of symmetry is more likely the structure of skorpionite, which shows that skorpionite is a ferroelectric mineral. The disordered structure is induced in skorpionite by twinning and/or domain structures because of the relaxation of the natural polarization caused by the arrangement of polarized water molecules. The space group Cc model without the center of symmetry eliminates the need for statistical distribution. Bond valence sum calculations and hydrogen bond networks can be explained in detail by the model. In the complicated structure caused by the chemical composition, the local structure with a non-ideal coordination environment is observed near the Zn sites. Hydrogen atoms are continuously arranged with regular arrangements of water molecules in the tunnel structure.