title: Semiclathrates of the Ge-P-Te system: synthesis and crystal structures.
abstract: Novel compounds [Ge(46-x) P(x) ]Te(y) (13.9≤x≤15.6, 5.92≤y≤7.75) with clathrate-like structures have been prepared and structurally characterized. They crystallize in the space group Fm ̅3 with the unit cell parameter changing from 20.544(2) to 20.698(2) Å (Z=8) on going from x=13.9 to x=15.6. Their crystal structure is composed of a covalently bonded Ge-P framework that hosts tellurium atoms in the guest positions and can be viewed as a peculiar variant of the type I clathrate superstructure. In contrast to the conventional type I clathrates, [Ge(46-x) P(x) ]Te(y) contain tricoordinated (3b) atoms and no vacancies in the framework positions. As a consequence of the transformation of the framework, the majority of the guest tellurium atoms form a single covalent bond with the host framework and thus the title compounds are the first representative of semiclathrates with covalent bonding. A comparison is made with silicon clathrates and the evolution of the crystal structure upon changing the tellurium content is discussed.
authors.affiliation: Chemistry of Department, Lomonosov Moscow State University, Leninskie Gory 1-3, Moscow 119991, Russia.
authors.forename: Maria A
authors.initials: MA
authors.lastname: Kirsanova
authors.forename: Liudmila N
authors.initials: LN
authors.lastname: Reshetova
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Olenev
authors.forename: Artem M
authors.initials: AM
authors.lastname: Abakumov
authors.forename: Andrei V
authors.initials: AV
authors.lastname: Shevelkov