Reassessment of Acceptor Passivation Models in p-Type Hydrogenated GaAs

1989 ◽  
Vol 163 ◽  
Author(s):  
I. Szafranek ◽  
G.E. Stillman
Keyword(s):  
Hydrogen Bond ◽  
Coulomb Interaction ◽  
Strong Interaction ◽  
Thermodynamic Stability ◽  
Relative Stability ◽  
Present Model ◽  
Bohr Radius ◽  
Microscopic Models ◽  
P Type ◽  
Relative Thermodynamic Stability

AbstractThe existing microscopic models of acceptor passivation in p-type hydrogenated GaAs are reviewed in light of new experimental results concerning the relative thermodynamic stability of the passivating complexes. In particular, the present model for neutralization of Group II acceptors, Be, Mg and Zn, on Ga sites is shown to be inadequate to account for the observed trends, which imply existence of a strong interaction between the hydrogen and acceptor. It is proposed that a direct acceptor-hydrogen bond is formed due to attractive Coulomb interaction between the ionized species. The relative stability of the pair complex can be then explained based on electronegativity of the acceptor species. Passivation at intermediate pair separations up to about twice the Bohr radius of the nearest acceptor, is also discussed.

scholarly journals Computer-Aided Insight into the Relative Stability of Enamines

Synthesis ◽  
2017 ◽  
Vol 49 (24) ◽  
pp. 5285-5306 ◽  
Author(s):  
Jaume Vilarrasa ◽  
Alejandro Castro-Alvarez ◽  
Héctor Carneros ◽  
Anna M Costa
Keyword(s):  
Relative Stability ◽  
Polar Solvent ◽  
Reaction Medium ◽  
Secondary Amines ◽  
Chiral Amines ◽  
Mo Calculations ◽  
Mannich Reactions ◽  
The Past ◽  
Relative Thermodynamic Stability ◽  
Insight Into

Venerable aldol, Michael, and Mannich reactions have undergone a renaissance in the past fifteen years, as a consequence of the development of direct organocatalytic versions, mediated by chiral amines. Chiral enamines are key intermediates in these reactions. This review focuses on the formation of enamines from secondary amines and their relative thermodynamic stability, as well as on the reverse reactions (hydrolysis). Experimental results and predictions based on MO calculations are reviewed to show which enamine forms may predominate in the reaction medium and to compare several secondary amines as organocatalysts.1 Introduction2 Relative Stability of Enamines as Determined Experimentally3 Pyrrolidine Enamines4 Enamines of the Jørgensen–Hayashi Catalyst5 Proline Enamines6 Free Enthalpies and Polar Solvent Effects7 Comparison of Organocatalysts8 Summary and Outlook9 Appendix

Energetics of Intra- and Inter-molecular Bonds in the Three Nitrophenols

1994 ◽  
Vol 47 (9) ◽  
pp. 1651 ◽  
Author(s):  
R Sabbah ◽  
M Gouali
Keyword(s):  
Thermal Analysis ◽  
Hydrogen Bond ◽  
Heat Capacity ◽  
Differential Thermal Analysis ◽  
Relative Stability ◽  
Intermolecular Bond ◽  
Resonance Energies ◽  
Heat Capacity Measurements ◽  
Intramolecular Hydrogen ◽  
Good Agreement

A thermodynamic study of the three nitrophenol isomers (general formula C6H5NO3) was realized by combustion calorimetry of small amounts of substance (a few milligrams), sublimation calorimetry, differential thermal analysis and heat capacity measurements. The experimental enthalpies of combustion, sublimation and fusion of these compounds are as follows: ortho para -ΔcH�m(s,298.15K)/kJ mol-1 2871.0�1.3 2875.1�0.9 2868.5�1.0 ΔsubH�m(298.15K)/kJ mol-1 72.30�0.28 91.23�0.49 92.39�0.43 ΔfusHm/kJ mol-1 18.32�0.35 20.54�0.34 17.33�0.10 Ttriple point/K 318.40�0.01 370.51�0.01 387.26�0.05   The strength of the intramolecular hydrogen bond in the ortho isomer was estimated equal to 20.09 kJ mol-1. The relative stability of the three isomers is discussed, and the intermolecular bond enthalpies have been determined. The experimental resonance energies Eexp,conj are 168.7, 142.8 and 148.2 kJ mol-1 for ortho -, meta- and para-nitrophenol respectively, and are in good agreement with theoretical values. The experimental atomization enthalpies Δa,expH°m(298.15K) are 6742.5�1.9, 6719.5�1.7 and 6724.9�1.8 kJ mol-1 for ortho -, meta- and para-nitrophenol respectively.

The effect of N-substituent on the relative thermodynamic stability of unionized and zwitterionic forms of α-diphenylphosphino-α-amino acids

2020 ◽  
Vol 30 (4) ◽  
pp. 516-518
Author(s):  
Olga S. Soficheva ◽  
Alina A. Nesterova ◽  
Alexey B. Dobrynin ◽  
Ekaterina M. Zueva ◽  
Joachim W. Heinicke ◽  
...  
Keyword(s):  
Amino Acids ◽  
Thermodynamic Stability ◽  
Relative Thermodynamic Stability

Supramolecular structure of 1H-pyrazoles in the solid state: a crystallographic and ab initio study

2000 ◽  
Vol 56 (6) ◽  
pp. 1018-1028 ◽  
Author(s):  
Concepción Foces-Foces ◽  
Ibon Alkorta ◽  
José Elguero
Keyword(s):  
Hydrogen Bond ◽  
Solid State ◽  
Secondary Structure ◽  
Ab Initio ◽  
Relative Stability ◽  
Quaternary Structure ◽  
Quantitative Model ◽  
Pyrazole Derivatives ◽  
Donor Group ◽  
Ab Initio Study

The secondary structure of 1H-unsubstituted pyrazole derivatives bearing only one hydrogen donor group and one or more acceptor groups has been analyzed in terms of some descriptors representing the substituents at C3 and C5. The substituent at C4 appears to affect mainly the tertiary or quaternary structure of these compounds. The proposed semi-quantitative model, which explains most hydrogen-bonded motifs as a combination of the effects of substituents at C3 and C5, has also been examined as a function of the steric and polarizability effects of these substituents represented by molar refractivity. The model also applies to other five-membered rings (1,2,4-triazoles, 1,2,4-diazaphospholes and 1,2,4-diazaarsoles). Furthermore, ab initio calculations at RHF/6-31G* have been performed to discover the relative stability of three of the four hydrogen-bond patterns displayed by several symmetrical pyrazoles (dimers, trimers, tetramers). The fourth motif, catemers, has only been discussed geometrically.

scholarly journals Synthesis, crystallisation and thermodynamics of two polymorphs of a new derivative of meglumine: 1-(2,2,3-trimethyl-1,3-oxazolidin-5-yl)-butane-1,2,3,4-tetrol

CrystEngComm ◽  
2018 ◽  
Vol 20 (1) ◽  
pp. 88-95 ◽  
Author(s):  
Michael Svärd ◽  
Gamidi Rama Krishna ◽  
Åke C. Rasmuson
Keyword(s):  
Thermodynamic Stability ◽  
Gibbs Energies ◽  
Relative Thermodynamic Stability

The structures of two polymorphs of a new compound have been determined, and the relative thermodynamic stability evaluated through comparison of their Gibbs energies of fusion.

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