Syntheses, Crystal and Electronic Structures, and Characterizations of Quaternary Antiferromagnetic Sulfides: Ba<sub>2</sub>MFeS<sub>5</sub> (M = Sb, Bi) Lei Geng Wen-Dan Cheng Hao Zhang Chen-Sheng Lin Wei-Long Zhang Ye-Yu Li Zhang-Zhen He 10.1021/ic102597y.s002 https://acs.figshare.com/articles/journal_contribution/Syntheses_Crystal_and_Electronic_Structures_and_Characterizations_of_Quaternary_Antiferromagnetic_Sulfides_Ba_sub_2_sub_MFeS_sub_5_sub_M_Sb_Bi_/2681068 Two new quaternary sulfides, Ba<sub>2</sub>SbFeS<sub>5</sub> and Ba<sub>2</sub>BiFeS<sub>5</sub>, were synthesized by using a conventional high-temperature solid-state reaction method in closed silica tubes at 1123 K. The two compounds both crystallize in the orthorhombic space group <i>Pnma</i> with <i>a</i> = 12.128(6) Å, <i>b</i> = 8.852(4) Å, <i>c</i> = 8.917(4) Å, and <i>Z</i> = 4 for Ba<sub>2</sub>SbFeS<sub>5</sub> and <i>a</i> = 12.121(5) Å, <i>b</i> = 8.913(4) Å, <i>c</i> = 8.837(4) Å, and <i>Z</i> = 4 for Ba<sub>2</sub>BiFeS<sub>5</sub>. The crystal structure unit can be viewed as an infinite one-dimensional edge-shared MS<sub>5</sub> (M = Sb, Bi) tetragonal-pyramid chain with FeS<sub>4</sub> tetrahedra alternately arranged on two sides of the MS<sub>5</sub> polyhedral chain via edge-sharing (so the chain can also be written as <sub>1</sub><sup>∞</sup>[MFeS<sub>5</sub>]<sup>4−</sup>). Interestingly, the compounds have the structural type of a Ba<sub>3</sub>FeS<sub>5</sub> high-pressure phase considering one Ba<sup>2+</sup> is replaced by one Sb<sup>3+</sup>/Bi<sup>3+</sup>, with Fe<sup>4+</sup> reduced to Fe<sup>3+</sup> for in order to maintain the electroneutrality of the system. As a result, the isolated iron ions in Ba<sub>3</sub>FeS<sub>5</sub> are bridged by intermediate MS polyhedra in Ba<sub>2</sub>MFeS<sub>5</sub> (M = Sb, Bi) compounds and form the <sub>1</sub><sup>∞</sup>[MFeS<sub>5</sub>]<sup>4−</sup> chain structure. This atom substitution of Ba<sup>2+</sup> by one Sb<sup>3+</sup>/Bi<sup>3+</sup> leads to a magnetic transition from paramagnetic Ba<sub>3</sub>FeS<sub>5</sub> to antiferromagnetic Ba<sub>2</sub>MFeS<sub>5</sub>, resulting from an electron-exchange interaction of the iron ions between inter- or intrachains. Magnetic property measurements indicate that the two compounds are both antiferromagnetic materials with Néel temperatures of 13 and 35 K for Ba<sub>2</sub>SbFeS<sub>5</sub> and Ba<sub>2</sub>BiFeS<sub>5</sub>, respectively. First-principles electronic structure calculations based on density functional theory show that the two compounds are both indirect-band semiconductors with band gaps of 0.93 and 1.22 eV for Ba<sub>2</sub>SbFeS<sub>5</sub> and Ba<sub>2</sub>BiFeS<sub>5</sub>, respectively. 2011-03-21 00:00:00 Quaternary Antiferromagnetic Sulfides antiferromagnetic Ba 2MFeS Magnetic property measurements space group Pnma Ba 3FeS crystal structure unit iron ions Ba 2MFeS Ba 2SbFeS FeS 4 tetrahedra Ba 2BiFeS MS 5 polyhedral chain