Vibrational frequencies of small selenium molecules

Reverse Monte Carlo simulations and Raman scattering of an amorphous GeSe4 alloy produced by mechanical alloying

“…On the other hand, this sequence in CS units has angles around 100 • , and n-fold rings have angles ranging from 92 • to 125 • . 18,46 The Θ Se-Ge-Ge (cos θ) and Θ Ge-Se-Se (cos θ) functions are similar to the others, having peaks at 58 • , associated with threefold rings, and at 116 • (Se-Ge-Ge) and 109 • (Ge-Se-Se), which are related to tetrahedral angles and n-fold rings. The Θ ijl (cos θ) functions above confirm that distorted tetrahedral units are formed in MA-a-GeSe 4 , with a clear preference for CS units.…”

“…1). The broad and intense band at 255 cm −1 is related to A 1 and E 2 modes of Se n rings 8,10,44,45,46 . It is important to note that the band at around 165 cm −1 , which is associated with Ge-Ge pairs vibrations in ethanlike units, is not seen in the spectrum of the alloy (as well as the other bands of c-Ge), indicating that the quantity of Ge-Ge pairs is very low in the alloy.…”

“…The Θ Se-Se-Se (cos θ) function has peaks at 55-61 • and a broad distribution from 99 to 118 • , with a maximum at 103 • . The internal Se-Se-Se angles in perfect tetrahedra are found at 60 • , the Se-Se-Se angle in trigonal Se is seen at 103 • and the angles in small Se chains and rings 46 can be found at 90-116 • . Thus, the Θ Se-Se-Se (cos θ) function indicates that the tetrahedra in MA-a-GeSe 4 are slightly distorted and Se chains and rings are formed, in agreement with RS results and with the previous analyses of the G ij (r) functions.…”

Selenium-loaded zeolite (ZSM-5): I. Structures and fundamental properties

“…On the other hand, the 380 cm −1 peak is assigned to a Se dimer, which is known to be stable in Se vapors. 9,10,20,24,25 We therefore conclude that Se in ZSM-5 takes chain structures, having negligible interchain interaction, and dimers.…”

“…However, in some studies, powderlike zeolites have been employed, which may exhibit substantial surface effects. 18,28,34 In addition, there is a variety of zeolites with pore shapes and covalencies, 5 while most of previous studies have employed zeolites containing ionic pores, [15][16][17][18][19][20][21][22][23][24][25][26][27][29][30][31][32][33][34] which may mask covalent properties of chalcogens. Accordingly, further work relating atomic structures with macroscopic properties in chalcogen-loaded covalent zeolites seems intriguing.…”