| Autor: |
Tassanov A; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States., Lee H; Department of Mechanical and Materials Engineering, Portland State University, Portland, Oregon 97201, United States., Xia Y; Department of Mechanical and Materials Engineering, Portland State University, Portland, Oregon 97201, United States., Hodges JM; Department of Chemistry, The Pennsylvania State University, University Park, Pennsylvania 16802, United States. |
| Abstrakt: |
Three new NaBa 2 M 3 Q 3 (Q 2 ) (M = Ag or Cu; Q = S or Se) chalcogenides were prepared by using solid-state methods and structurally characterized by using single-crystal X-ray diffraction. NaBa 2 Ag 3 Se 3 (Se 2 ) and NaBa 2 Cu 3 Se 3 (Se 2 ) crystallize in monoclinic space group C 2/ m and have a two-dimensional structure composed of edge-sharing MSe 4/4 tetrahedra separated by Na + and Ba 2+ cations, along with (Se 2 ) 2- dimers at the center of the spacings between [M 3 Se 3 ] 3- slabs. NaBa 2 Ag 3 S 3 (S 2 ) adopts a related structure with space group C 2/ m but has additional, crystallographically distinct Ag atoms in the [Ag 3 S 3 ] 3- layer that are linearly coordinated. NaBa 2 Ag 3 Se 3 (Se 2 ) and NaBa 2 Ag 3 S 3 (S 2 ) have indirect band gaps measured to be 1.2 and 1.9 eV, respectively, which is supported by band structures calculated using density functional theory. Mixed-anion NaBa 2 Cu 3 Se 5- x S x compositions were prepared to probe the presence of anion ordering and heteronuclear (S-Se) 2- dimers. Structural analyses of the sulfoselenides indicate that selenium preferentially occupies the Q-Q dimer sites, while Raman spectroscopy reveals a mixture of (S 2 ), (Se 2 ), and heteronuclear (S-Se) units in the sulfur-rich products. The local ordering of the chalcogens is rationalized using simple bonding concepts and adds to a growing framework for understanding ordering phenomena in mixed-anion systems. |
