Second moment scaling and the relationship of geometric and electronic structure
Extended Hueckel band calculations were used to show the ditellurides in the CdI[sub 2] structure type with more than 16 valence electrons/MTe[sub 2] unit should have an instability due to their electronic structure. Single crystal X-ray diffraction studies of the electron rich Ta[sub 1[minus]x]Ti[sub x]Te[sub 2] (x = 0.2, 0.3, 0.4 and 0.5) show that a statistical distortion of the CdI[sub 2] structure type has indeed occurred for these compounds confirming the theoretical calculations. Second Moment Scaled Hueckel theory was used to examine the basis of the Hume-Rothery phases are face centered cubic, hexagonal closest packed ([zeta], [epsilon] and [eta]-hcp), body centered cubic, [beta]-Mn and [gamma]-brass structures. Good agreement between the experimental and theoretically predicted electron concentration ranges was achieved when an s, p and contracted d orbital model was used. The results presented in this thesis were the first theoretical calculations that corroborate the entire set of Hume-Rothery electron concentration rules. Second Moment Scaled Hueckel energies were used for constructing structure maps for intermetallic compounds with stoichiometry ZA[sub 2], ZA[sub 3] and ZA[sub 6]. Calculations were performed only on the covalent network of the A atoms. The structure types considered were SmSb[sub 2], ZrSi[sub 2], Cu[sub 2]Sb, AuCu[sub 3], TiNi[sub 3], TiCu[sub 3], BiF[sub 3], SnNi[sub 3], NdTe[sub 3], TiS[sub 3], SmAu[sub 6], CeCu[sub 6] and PuGa[sub 6]. The bond distance variation found for closo-borohydrides B[sub 8]H[sub 8][sup 2[minus]], B[sub 9]H[sub 9][sup 2[minus]], and B[sub 10]H[sub 10][sup 2[minus]] and the transition metal carbonyls; Re[sub 4] (CO)[sub 16][sup 2[minus]], Os[sub 5](CO)[sub 16], and IR[sub 4](CO)[sub 16] was accounted for using Second Moment Scaling technique. These calculations resolved the differences in energies of the closo, nido, and arachno borohydride cluster forms.
- Research Organization:
- Michigan Univ., Ann Arbor, MI (United States)
- OSTI ID:
- 6908754
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
360102 -- Metals & Alloys-- Structure & Phase Studies
664100* -- Theory of Electronic Structure of Atoms & Molecules-- (1992-)
74 ATOMIC AND MOLECULAR PHYSICS
ALLOYS
CALCULATION METHODS
CHALCOGENIDES
COHERENT SCATTERING
CRYSTAL STRUCTURE
DATA
DIFFRACTION
ELECTRONIC STRUCTURE
INFORMATION
INTERMETALLIC COMPOUNDS
MOLECULAR ORBITAL METHOD
NUMERICAL DATA
PLATINUM METAL ALLOYS
SCATTERING
TELLURIDES
TELLURIUM COMPOUNDS
THEORETICAL DATA
X-RAY DIFFRACTION