Eu3(AsS4)2 and AxEu3-yAs5-zS10 (A=Li, na):: Compounds with simple and complex thioarsenate building blocks

Eu-3(AsS4)(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 As5+ and AS(3+) centers, respectively. The rhombohedral EU3(AsS4)2 features a new structure type consisting of eight-coordinate Eu2+ centers and AsS43- anions, whereas the monoclinic AxEu(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 [As10S20](10-) segments linked with EU2+ 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)"-