Beschreibung:
<jats:title>Abstract</jats:title>
<jats:p>Idiomorphous crystals of five different polymorphic modifications (α-ε) of TeI<jats:sub>4</jats:sub> are simultaneously grown from solutions of TeI<jats:sub>4</jats:sub> and concentrated HI in methanol by evaporating the solvent at room temperature. δ-TeI<jats:sub>4</jats:sub> is the only stable phase at normal conditions. Phase transformations of α-, β-, γ-and ε-TeI<jats:sub>4</jats:sub> to the final stage δ-TeI<jats:sub>4</jats:sub> take place by heating and run through discrete intermediates. The observed graduations lead to a sequence γ-, β-, α-,ε-TeI<jats:sub>4</jats:sub> which indicates “increasing metastability”. The crystal structures of α-TeI<jats:sub>4</jats:sub> (trigonal; P3̄ml; a = 4.228(2), c - 6.684(6)Å, Z = 0.5; D<jats:sub>x</jats:sub> = 5.10 g/cm<jats:sup> 3</jats:sup>), β-TeI<jats:sub>4</jats:sub> (orthorhombic; Pn2<jats:sub>1</jats:sub>m; a = 6.888(2), b = 14.539(3), c = 16.753(4) Å, Z = 8; D<jats:sub>x</jats:sub> = 5.03 g/cm<jats:sup>3</jats:sup>) and γ-TeI<jats:sub>4</jats:sub> (monoclinic; P2<jats:sub>1</jats:sub>/c; a = 11.199(4), b = 13.599(4), c = 22.158(6) Å,β = 98.10(3)°, Z = 16; D, = 5.05 g/cm<jats:sup>3</jats:sup>) are related to the known crystal structure of δ-TeI<jats:sub>4</jats:sub>. α-TeI<jats:sub>4</jats:sub> (“Te<jats:sub>0.5</jats:sub>I<jats:sub>2</jats:sub>”) is an isotype of the 2H-CdI : structure with random distribution of Te over the Cd-positions. The crystal structures of β-, γ-and δ-TeI 4 contain discrete tetrameric molecules “(TeI<jats:sub>4</jats:sub>)<jats:sub>2</jats:sub> (TeI<jats:sub>3</jats:sub>
<jats:sup>+</jats:sup>I<jats:sup>-</jats:sup>)<jats:sub>2</jats:sub>” which are generated by ordered distributions of Te over 1/4 of the octahedral holes of a 2H-(β) and a 4H-sequence (y,δ ) of the nearly close packed iodine layers. A nearly cubic close packing of Iodine atoms is observed in the crystal structure of ε-TeI<jats:sub>4</jats:sub> (tetragonal; I4<jats:sub>1</jats:sub>/amd; a = 16.875(6), c -11.829(5) Å, Z = 16; D<jats:sub>x</jats:sub> = 5.01 g/cm <jats:sup>3</jats:sup>). The ordered distribution of Te in 1/4 of the octahedral holes leads to tetrameric molecules “(TeI<jats:sub>3</jats:sub>
<jats:sup>+</jats:sup>I<jats:sup>-</jats:sup>)<jats:sub>4</jats:sub>” in a cubanelike arrangement which, thus far, has been observed only in the crystal structures of TeCl<jats:sub>4</jats:sub> and TeBr<jats:sub>4</jats:sub> . The Madelung Parts of Lattice Energies, MAPLE, of β-, γ-, δ-and ε-TeI<jats:sub>4</jats:sub> are calculated. </jats:p>