Structural and Thermodynamic Stability of the “1111” Structure Type: A Case Study of the EuFZnPn Series

Two new compounds with the LaOAgS structure, EuFZnAs (<b>1</b>) and EuFZnSb (<b>2</b>), were obtained via solid state reaction. Both compounds are tetragonal (<i>P</i>4/<i>nmm</i>) with the cell parameters <i>a</i> = 4.1000(1) Å and <i>c</i> = 9.0811(1) Å for <b>1</b> and <i>a</i> = 4.2852(1)­Å and <i>c</i> = 9.4238(1)­Å for <b>2</b>. The absence of their phosphide analog can be explained based on crystal chemical considerations as well as on quantum-chemical estimates of their thermodynamic stability with respect to EuF₂ and EuZn₂Pn₂. The magnetic response of <b>1</b> and <b>2</b> is ascribed to the presence of Eu²⁺ ions. Both compounds are paramagnetic down to low temperatures, where they order antiferromagnetically at ∼5 K and ∼3 K, respectively. They are narrow-gap semiconductors, and EuFZnSb demonstrates a relatively high value of the Seebeck coefficient

Two New Arsenides, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, With a New Filled Variety of the BaHg₁₁ Structure

Two new ternary arsenides, namely, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg₁₁ motif with cubic voids alternately occupied by Eu­(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group <i>Fm</i>3̅<i>m</i>, <i>a</i> = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity

Two New Arsenides, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, With a New Filled Variety of the BaHg₁₁ Structure

Two new ternary arsenides, namely, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg₁₁ motif with cubic voids alternately occupied by Eu­(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group <i>Fm</i>3̅<i>m</i>, <i>a</i> = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity

Two New Arsenides, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, With a New Filled Variety of the BaHg₁₁ Structure

Two new ternary arsenides, namely, Eu₇Cu₄₄As₂₃ and Sr₇Cu₄₄As₂₃, were synthesized from elements at 800 °C. Their crystal structure represents a new filled version of the BaHg₁₁ motif with cubic voids alternately occupied by Eu­(Sr) and As atoms, resulting in a 2 × 2 × 2 superstructure of the aristotype: space group <i>Fm</i>3̅<i>m</i>, <i>a</i> = 16.6707(2) Å and 16.7467(2) Å, respectively. The Eu derivative exhibits ferromagnetic ordering below 17.5 K. In agreement with band structure calculations both compounds are metals, exhibiting relatively low thermopower, but high electrical and low thermal conductivity