Eu₃(AsS₄)₂ and A<i>_x</i>Eu₃_-<i>_y</i>As₅_-<i>_z</i>S₁₀ (A = Li, Na): Compounds with Simple and Complex Thioarsenate Building Blocks

Abstract

Eu(3)(AsS(4))(2) and A(x)Eu(3-y)As(5-z)S(10) (A = Li, Na) are the members of a new thioarsenate family. They feature As(5+) and As(3+) centers, respectively. The rhombohedral Eu(3)(AsS(4))(2) features a new structure type consisting of eight-coordinate Eu(2+) centers and AsS(4)(3-) anions, whereas the monoclinic A(x)Eu(3-y)As(5-z)S(10) (Li(0.73)Eu(3)As(4.43)S(10) and Na(0.66)Eu(2.86)As(4.54)S(10)) belong to the rathite sulfosalt family and are comprised of apparent [As(10)S(20)](10-) segments linked with Eu(2+) ions to give a three-dimensional network. They appear to be alkali-metal-stabilized derivatives of the putative parent phase "Eu(3)As(5)S(10)".