Electronic structure and thermodynamics of scandium monosulfide

Technical Report · Wed Aug 01 04:00:00 EDT 1984

OSTI ID:6612259

Nakahara, J F

The self-consistent, nonrelativistic band structure calculations, employing the KKR Green's function method, were performed for stoichiometric Sc/sub 1/ /sub 00/S and a hypothetical ordered defect compound of composition Sc/sub 3/S/sub 4/. When metal atom vacancies are introduced, (a) the wavefunctions associated with the sulfur atom near a vacancy are redistributed, inducing nonbonding p-states and (b) the covalency of the metal-nonmetal bonding interaction is enhanced, resulting in an unchanged scandium valency. Analysis of the charge density suggests that the primary metal-metal bonding interaction is directed through the octahedral faces of the sulfur polyhedron, while a secondary interaction is directed through the edges. Vacancy formation and stabilization are thought to be energetically driven but the exact nature has not been determined. The high temperature vaporization of a scandium-rich monosulfide was investigated by the mass loss Knudsen effusion method. The homogeneity range was found to extend into the metal-rich region, as far as Sc/sub 1/ /sub 14/S, as determined by the rapid decrease in the Sc partial pressure at the start of a run. The activity of ScS in Sc/sub 0/ /sub 8065/S(s) was determined to be 0.48 +- 0.05 and is constant at 1950 to 2100/sup 0/K. The energy required to create approximately 20% scandium vacancies in ScS is 25.0 +- 1.8 kcal mol/sup -1/ at 298/sup 0/K. A third-law temperature independent enthalpy of atomization at 298/sup 0/K of ScS is 255.7 +- 2.6 kcal mol/sup -1/ and the enthalpy of formation at 298/sup 0/K of ScS is -98.7 +- 2.8 kcal mol/sup -1/.

• Research Organization: Ames Lab., IA (USA)
• DOE Contract Number: W-7405-ENG-82
• OSTI ID: 6612259
• Report Number(s): IS-T-1133; ON: DE84015259
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
400201* -- Chemical & Physicochemical Properties
CHALCOGENIDES
ELECTRONIC STRUCTURE
EVAPORATION
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
SCANDIUM COMPOUNDS
SCANDIUM SULFIDES
SULFIDES
SULFUR COMPOUNDS
THERMODYNAMIC PROPERTIES
TRANSITION ELEMENT COMPOUNDS
VAPOR PRESSURE