These tools will no longer be maintained as of December 31, 2024. Archived website can be found here. PubMed4Hh GitHub repository can be found here. Contact NLM Customer Service if you have questions.


Pubmed for Handhelds

PUBMED FOR HANDHELDS

Search MEDLINE/PubMed

  • Title: Impressive structural diversity and polymorphism in the modular compounds ABi3Q5 (A = Rb, Cs; Q = S, Se, Te).
    Author: Iordanidis L, Bilc D, Mahanti SD, Kanatzidis MG.
    Journal: J Am Chem Soc; 2003 Nov 12; 125(45):13741-52. PubMed ID: 14599213.
    Abstract:
    An outstanding example of structural diversity and complexity is found in the compounds with the general formula ABi(3)Q(5) (A = alkali metal; Q = chalcogen). gamma-RbBi(3)S(5) (I), alpha-RbBi(3)Se(5) (II), beta-RbBi(3)Se(5) (III), gamma-RbBi(3)Se(5) (IV), CsBi(3)Se(5) (V), RbBi(3)Se(4)Te (VI), and RbBi(3)Se(3)Te(2) (VII) were synthesized from A(2)Q (A = Rb, Cs; Q = S, Se) and Bi(2)Q(3) (Q = S, Se or Te) at temperatures above 650 degrees C using appropriate reaction protocols. gamma-RbBi(3)S(5) and alpha-RbBi(3)Se(5) have three-dimensional tunnel structures while the rest of the compounds have lamellar structures. gamma-RbBi(3)S(5), gamma-RbBi(3)Se(5), and its isostructural analogues RbBi(3)Se(4)Te and RbBi(3)Se(3)Te(2) crystallize in the orthorhombic space group Pnma with a = 11.744(2) A, b = 4.0519(5) A, c = 21.081(3) A, R1 = 2.9%, wR2 = 6.3% for (I), a = 21.956(7) A, b = 4.136(2) A, c = 12.357(4) A, R1 = 6.2%, wR2 = 13.5% for (IV), and a = 22.018(3) A, b = 4.2217(6) A, c = 12.614(2) A, R1 = 6.2%, wR2 = 10.3% for (VI). gamma-RbBi(3)S(5) has a three-dimensional tunnel structure that differs from the Se analogues. alpha-RbBi(3)Se(5) crystallizes in the monoclinic space group C2/m with a = 36.779(4) A, b = 4.1480(5) A, c = 25.363(3) A, beta = 120.403(2) degrees, R1 = 4.9%, wR2 = 9.9%. beta-RbBi(3)Se(5) and isostructural CsBi(3)Se(5) adopt the space group P2(1)/m with a = 13.537(2) A, b = 4.1431(6) A, c = 21.545(3) A, beta = 91.297(3) degrees, R1 = 4.9%, wR2 = 11.0% for (III) and a = 13.603(3) A, b = 4.1502(8) A, c = 21.639(4) A, beta = 91.435(3) degrees, R1 = 6.1%, wR2 = 13.4% for (V). alpha-RbBi(3)Se(5) is also three-dimensional, whereas beta-RbBi(3)Se(5) and CsBi(3)Se(5) have stepped layers with alkali metal ions found disordered in several trigonal prismatic sites between the layers. In gamma-RbBi(3)Se(5) and RbBi(3)Se(4)Te, the layers consist of Bi(2)Te(3)-type fragments, which are connected in a stepwise manner. In the mixed Se/Te analogue, the Te occupies the chalcogen sites that are on the "surface" of the layers. All compounds are narrow band-gap semiconductors with optical band gaps ranging 0.4-1.0 eV. The thermal stability of all phases was studied, and it was determined that gamma-RbBi(3)Se(5) is more stable than the and alpha- and beta-forms. Electronic band calculations at the density functional theory (DFT) level performed on alpha-, beta-, and gamma-RbBi(3)Se(5) support the presence of indirect band gaps and were used to assess their relative thermodynamic stability.
    [Abstract] [Full Text] [Related] [New Search]