scholarly journals X-ray diffraction and theoretical study of the transition 2H-3R polytypes in Nb1+xSe2 (0 < x < 0.1)

2021 ◽  
Vol 3 ◽  
pp. e2
Author(s):  
Mohamed Sidoumou ◽  
Soumia Merazka ◽  
Adrian Gómez-Herrero ◽  
Mohammed Kars ◽  
Roisnel Thierry
Keyword(s):  
Single Crystals ◽  
Theoretical Study ◽  
Stoichiometric Composition ◽  
Chemical Transport ◽  
X Ray Diffraction ◽  
Chemical Transport Reaction ◽  
Transport Reaction ◽  
X Ray ◽  
Trigonal Prismatic Coordination ◽  
Trigonal Prismatic

Single crystals of 2H and 3R niobium diselenide were grown by a chemical transport reaction. The current determinations by single crystals X-ray diffraction reveal a non-stoichiometric composition. The structures are built from Se—Nb—Se slabs with Nb in trigonal prismatic coordination whereas the extra or additional Nb atoms are located in the octahedral holes between the slabs giving rise to the formula 2H and 3R-Nb1+xSe2 with 0.07 < x < 0.118. In particular, vacancy and Nb-Nb interactions may play an important role on the non-stoichiometry and the stacking mode in NbSe2. By increasing the number of additional Nb atoms in the pure 2H-NbSe2, a transition 2H to 3R polytype should occur in order to minimize the Nblayer—Nbextra—Nblayer repulsions between these adjacent slabs. The theoretical study shows that both 2H and 3R-Nb1+xSe2 are thermodynamically stable in the range 0 < x < 0.1.

Sr4Pt10In21 – the first representative of the Ho4Ni10In21 type with a divalent cation

2019 ◽  
Vol 74 (5) ◽  
pp. 443-449 ◽  
Author(s):  
Birgit Heying ◽  
Jutta Kösters ◽  
Rainer Pöttgen
Keyword(s):  
Single Crystal ◽  
Single Crystals ◽  
Glassy Carbon ◽  
Divalent Cation ◽  
High Frequency ◽  
Three Dimensional ◽  
X Ray ◽  
Trigonal Prismatic Coordination ◽  
Trigonal Prismatic

AbstractRod-shaped single crystals of Sr4Pt10In21were prepared from the elements in glassy-carbon crucibles in a high-frequency furnace. The structure of Sr4Pt10In21was refined from single-crystal X-ray diffractometer data:C2/m, Ho4Ni10Ga21type,a = 2322.62(7),b = 450.27(2),c = 1958.09(7) pm,β = 133.191(3)°,wR = 0.0464, 3200F2values and 107 variables. The three-dimensional [Pt10In21]δ−polyanionic network is stabilized through substantial Pt–In (269–313 pm Pt–In) and In–In (294–362 pm In–In) bonding. All platinum atoms have slightly distorted tri-capped trigonal prismatic coordination and the two crystallographically independent strontium atoms are located in penta-capped pentagonal prisms.

On the preparation of Fe7Se8 single crystals by a chemical transport reaction

1974 ◽  
Vol 9 (9) ◽  
pp. 1267-1272 ◽  
Author(s):  
A. Paja̧czkowska ◽  
P. Peshev ◽  
M. Ivanova ◽  
R. Gałazka
Keyword(s):  
Single Crystals ◽  
Chemical Transport ◽  
Chemical Transport Reaction ◽  
Transport Reaction

Absorption spectra of Co2+ in AgInS2 orthorhombic single crystals

2001 ◽  
Vol 16 (4) ◽  
pp. 975-978 ◽  
Author(s):  
Hidong Kim ◽  
Seok-Joo Lee ◽  
Jae-Eun Kim ◽  
Hae Yong Park ◽  
Seok-Kyun Oh ◽  
...  
Keyword(s):  
Single Crystals ◽  
Absorption Spectra ◽  
Chemical Transport ◽  
Spin Orbit Coupling ◽  
Spin Orbit ◽  
Chemical Transport Reaction ◽  
Transport Reaction ◽  
Electronegativity Difference ◽  
Crystal Field Parameters ◽  
The Ideal

The optical absorption spectra of AgInS2:Co2+ single crystals grown by chemical transport reaction using iodine as a transporting medium have been studied at 6 K. The peaks can be explained by the transitions of Co2+ in the Td symmetry with the spin-orbit coupling, which means that the deviations of the atomic sites from those of the ideal wurtzite structure can be considered negligibly small. The consideration of both the crystal field parameters and the electronegativity difference between atoms may indicate that Co atoms substitute In atoms.

scholarly journals Equiatomic iron-based tetrelides TFeSi and TFeGe (T = Zr, Nb, Hf, Ta) – A 57Fe Mössbauer-spectroscopic study

2019 ◽  
Vol 74 (2) ◽  
pp. 211-219 ◽  
Author(s):  
Sebastian Stein ◽  
Theresa Block ◽  
Steffen Klenner ◽  
Lukas Heletta ◽  
Rainer Pöttgen
Keyword(s):  
Room Temperature ◽  
Structural Motif ◽  
Clear Correlation ◽  
X Ray Diffraction ◽  
X Ray ◽  
Arc Melting ◽  
Structural Distortions ◽  
Trigonal Prismatic Coordination ◽  
The Common ◽  
Trigonal Prismatic

AbstractThe equiatomic iron-silicides TFeSi as well as the corresponding germanides TFeGe with the electron-poor 4d and 5d transition metals (T=Zr, Nb, Hf, Ta) have been synthesized from the elements by arc-melting. All samples were characterized through their lattice parameters using powder X-ray diffraction (Guinier technique). Four structures were refined from single-crystal X-ray diffractometer data: a=640.16(3), b=393.45(5), c=718.42(6) pm, Pnma, 390 F2 values, 20 parameters, wR2=0.0294 for ZrFeSi (TiNiSi type), a=719.63(11), b=1119.27(7), c=649.29(7) pm, Ima2, 1103 F2 values, 54 parameters, wR2=0.0555 for NbFeGe (TiFeSi type), a=655.96(7), c=372.54(4) pm, P6̅2m, 251 F2 values, 15 parameters, wR2=0.0260 for HfFeGe (ZrNiAl type) and a=624.10(3), b=378.10(6), c=725.25(7) pm, Pnma, 369 F2 values, 20 parameters, wR2=0.0513 for TaFeGe (TiNiSi type). The common structural motif of the four different structures is the slightly distorted tetrahedral tetrel (tr) coordination of the iron atoms and a trigonal prismatic coordination of iron by T=Zr, Nb, Hf, Ta. Three compounds were characterized as Pauli-paramagnetic by measuring their susceptibility. The measurement of the electrical resistivity of NbFeSi characterises this compound as a good metal. Furthermore, 57Fe Mössbauer spectra of all compounds could be obtained at room temperature, revealing a clear correlation between the structural distortions and the quadrupole splitting parameters.

On the preparation of Cr2O3 single crystals by a chemical transport reaction

1973 ◽  
Vol 8 (9) ◽  
pp. 1011-1020 ◽  
Author(s):  
P. Peshev ◽  
G. Bliznakov ◽  
G. Gyurov ◽  
M. Ivanova
Keyword(s):  
Single Crystals ◽  
Chemical Transport ◽  
Chemical Transport Reaction ◽  
Transport Reaction
Sign in / Sign up

Export Citation Format

Share Document