Thermochemistry of (germanium + selenium) : a review and critical assessment.

Journal Article · Wed May 01 04:00:00 EDT 1996 · J. Chem. Thermodyn.

DOI:https://doi.org/10.1006/jcht.1996.0045· OSTI ID:937819

O'Hare, P A. G.; Zywocinski, A; Curtiss, L A; NIST,

This review deals with the critical assessment of the thermodynamic properties of several germanium selenides: GeSe(cr), GeSe(g), GeSe{sub 2}(cr), GeSe{sub 2}(g). In the absence of experimental information, the structures, internuclear distances, and vibrational wavenumbers were calculated for GeSe{sub 2}(g) and Ge{sub 2}Se{sub 2}(g) by molecular orbital methods. The triatomic GeSe{sub 2}(g) is linear. The T{prime} tetratomic selenide has a butterfly-shaped structure, with alternating Ge and Se atoms, akin to Ge{sub 2}S{sub 2}(g) but the interplanar angle, close to 0.78{center_dot}{pi}, is smaller than in the sulfur-containing analog. Statistical mechanical methods were used to calculate the conventional molar thermodynamic functions {l_brace}C{sub p,m}{sup o}(T), {Delta}{sub 0}{sup T}S{sub m}{sup o}, {Delta}{sub T}{sup T},H{sub m}{sup o}, and {phi}{sub m}{sup o}(T){r_brace} of GeSe, GeSe{sub 2}, and Ge{sub 2}Se{sub 2} in the ideal gas state at a pressure p{sup o}= 101.325 kPa with T{prime}= 298.15 K. Heat capacities of solid GeSe and GeSe{sub 2} reported in the literature were re-evaluated from T{yields} 0 to the melting temperatures. The enthalpy of sublimination {Delta}{sub sub}H{sub m}{sup o}(GeSe, 298.15 K) is selected as (172.7 {+-} 1.0) kJ{center_dot}mol{sup -1} on the basis of a third-law evaluation of published vapor pressure measurements. A similar treatment yielded {Delta}{sub r}H{sub m}{sup o}(298.15 K) = (295.8 {+-} 1.0) kJ x mol{sup -1} for the reaction: GeSe{sub 2}(cr) = GeSe(g) + ({sup 1}{sub 2})Se{sub 2}(g). For dissociation of Ge{center_dot}Se bonds, enthalpies D{sub m}{sup o}, and mean enthalpies <D{sub m}{sup o}>, were calculated to be: D{sub m}{sup o}(GeSe) = (480.6 {+-} 1.7) kJ{center_dot}mol{sup -1} at T{yields} 0; <D{sub m}{sup o}>(GeSe{sub 2}) = (364 {+-} 9)kJ{center_dot}mol, and <D{sub m}{sup o}>(GeSe{sub 2}Se{sub 2}) = 270 {+-} 2 kJ{center_dot}mol{sup -1}, both at T= 298.15 K. The trend in values of enthalpies of dissociation parallels the nominal bond orders.

• Research Organization: Argonne National Laboratory (ANL)
• DOE Contract Number: AC02-06CH11357
• OSTI ID: 937819
• Report Number(s): ANL/CMT/JA-21068
• Journal Information: J. Chem. Thermodyn., Journal Name: J. Chem. Thermodyn. Journal Issue: 5 ; May 1996 Vol. 28; ISSN JCTDAF; ISSN 0021-9614
• Country of Publication: United States
• Language: ENGLISH

Related Subjects

36 MATERIALS SCIENCE
DISSOCIATION HEAT
GERMANIUM SELENIDES
MOLECULAR ORBITAL METHOD
MOLECULAR STRUCTURE
SPECIFIC HEAT
SUBLIMATION HEAT
THERMODYNAMIC PROPERTIES