Gas and solution phase thermochemistry and transition energies of NH2• and NH3•+, and their aquo complexes: an ab initio study

1994 ◽  
Vol 72 (3) ◽  
pp. 471-483 ◽  
Author(s):  
Dake Yu ◽  
Arvi Rauk ◽  
David A. Armstrong
Keyword(s):  
Ab Initio ◽  
Binding Energies ◽  
Solution Phase ◽  
Interaction Energies ◽  
Free Energies ◽  
Transition Energies ◽  
Bonding Interaction ◽  
Ab Initio Structure ◽  
Total Energies ◽  
Free Energy Of Solution

Ab initio calculations were performed on several aquo complexes of NH2•, and NH3•+, and on monomeric parent species. The geometries were optimized at the HF/6-31 + G* level and the vibrational frequencies were calculated. The total energies and the binding energies of complexes were evaluated at the MP2/6-31 + G* + ZPE level of theory. Gas and aqueous solution phase thermodynamic properites of NH2• and NH3•+ and several other species were calculated. The examination of solution phase properties of the radicals was facilitated by study of the structures and transition energies of aquo complexes. H-bonding interaction energies decreased in the order [Formula: see text] but were generally stronger than σ–σ* interactions involving the unpaired electron. From calculations with the CIS method, the weak absorption observed at 520 nm for aqueous NH2• is confirmed as a 2B1 → 2A1 transition, while the stronger NH2• absorption occurring below 250 nm and the absorption of NH3•+, which rises monotonically below 370 nm, are attributed to solvent-to-solute charge transfer bands. The solution free energies and related E0 values for NH2• and NH3•+ are in agreement with those of Stanbury. The ab initio structure studies show that water protons are bound to N, and proton transfer from solvent in reaction [18], NH2• + e− + H2O → NH3 + OH−, is likely to be the dominant redox reaction of NH2• in alkaline solution. The free energy of solution of NH3•+ is shown to be larger than that of [Formula: see text].

A comparison of ab initio quantum-mechanical and experimental D0 binding energies of eleven H-bonded and eleven dispersion-bound complexes

2015 ◽  
Vol 17 (40) ◽  
pp. 26645-26652 ◽  
Author(s):  
Susanta Haldar ◽  
Ramachandran Gnanasekaran ◽  
Pavel Hobza
Keyword(s):  
Ab Initio ◽  
Zero Point ◽  
Binding Energies ◽  
Quantum Mechanical ◽  
Interaction Energies ◽  
Dissociation Energies ◽  
Vibrational Energies

Dissociation energies (D0) of 11 H-bonded and 11 dispersion-bound complexes were calculated as the sum of interaction energies and the change of zero-point vibrational energies (ΔZPVE).

Stable Structures of Donor-Acceptor-Donor Trimer Codopants in 4H-SiC

2013 ◽  
Vol 718-720 ◽  
pp. 37-41
Author(s):  
Naoyuki Nishio ◽  
Masanori Miyata ◽  
Yoshinori Hayafuji
Keyword(s):  
Ab Initio ◽  
Concentration Ratio ◽  
Binding Energies ◽  
Donor Acceptor ◽  
Total Energies ◽  
Formation Energies ◽  
Doping Condition ◽  
Stable Structures

The total energies of 4H-SiC with donor-acceptor-donor (D2A) trimer codopants (D = N, P, As, and Sb, A = B, Al, Ga, and In), the formation energies of D2A, DA, D, and A species and the binding energies were studied usingab initiocalculations in order to determine the stable structures of D2A trimer codopants in 4H-SiC. The results of the calculations indicated that some of the trimer codopants were formed and were stable in 4H-SiC. In particular, N2Al, N2Ga and N2In trimer codopants with N(Ch)-Al/Ga/In (Sik)-N(Ch) configuration and As2B trimer codopants with As (Sih)-B(Ck)-As (Sih) configuration stably exist in 4H-SiC under the doping condition wherein the concentration ratio of donors to acceptors is 2 : 1.

DIRECT INTERACTION ENERGY: A COMPUTATIONAL QUANTITY FOR PARAMETERIZATION OF CONDENSED-PHASE FORCE FIELDS AND ITS APPLICATION TO HYDROGEN BONDING

2005 ◽  
Vol 04 (spec01) ◽  
pp. 689-705 ◽  
Author(s):  
ZHI-XIANG WANG ◽  
YONG DUAN
Keyword(s):  
Hydrogen Bonding ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Direct Interaction ◽  
Polarizable Continuum Model ◽  
Binding Energies ◽  
Water Dimer ◽  
Free Energies ◽  
Model Complexes ◽  
Solvent Polarization

Using N-Methylacetamide (NMA) dimer and NMA–water as model complexes, the solvent effect on the protein inter- N – H ⋯ O =C and intra- N – H ⋯ OH 2, and C = O ⋯ H 2 O hydrogen bonding have been studied by the polarizable continuum model (PCM) ab initio calculations in the four media (vacuum, ether, nitromethane and water). In contrast to the empirical approaches, we suggested using the direction interaction energies (DE) to consider the solvent polarization, which can be derived from PCM ab initio calculations. The DEs of the model compounds in solvents are larger than their in vacuo binding energies, which reflect the solvent polarization effect. As the solvents become increasingly polar, the binding free energies decrease while DEs increase. The increasing DE is consistent with the increasing hydrogen bond length. Considering the protein environment, the DEs of NMA-NMA dimer in ether, 9.14 and 9.41 kcal/mol for NMADI and NMADII, are recommended for the intra N – H ⋯ O =C hydrogen bonding. The DEs of NMA–water complex in water, -5.47 (NMAWI) and -5.41 kcal/mol (NMAWI'), -8.44 (NMAWII) and -8.68 kcal/mol (NMAWII'), respectively, are suggested for the inter- N – H ⋯ OH 2 and C – O ⋯ H 2 O hydrogen bonding of proteins. Using the same approach, we have also computed the DE of water dimer in liquid water. The computed DE of water dimer (-5.63 kcal/mol) is larger than the in vacuo water dimerization energy (-5.14 kcal/mol) and in reasonable agreement with the dimerization energies (ranging from –6.0 to 6.8 kcal/mol) of polarization-included empirical water models.

Ab initio structure determination of cytochrome c6 by combined reciprocal space-real space approach

2003 ◽  
Vol 218 (1) ◽  
Author(s):  
K. Chowdhury ◽  
S. Ghosh ◽  
M. Mukherjee
Keyword(s):  
Cytochrome C ◽  
Ab Initio ◽  
Structure Determination ◽  
Direct Method ◽  
Real Space ◽  
Reciprocal Space ◽  
Cytochrome C6 ◽  
Ab Initio Structure ◽  
Space Approach

AbstractThe direct method program SAYTAN has been applied successfully to redetermine the structure of cytochrome c

Ion solvation by dipolar aprotic solvents. An ab initio study

1987 ◽  
Vol 52 (1) ◽  
pp. 6-13 ◽  
Author(s):  
Petr Kyselka ◽  
Zdeněk Havlas ◽  
Ivo Sláma
Keyword(s):  
Ab Initio ◽  
Geometry Optimization ◽  
Molecular Structures ◽  
Dimethyl Sulphoxide ◽  
Ion Solvation ◽  
Interaction Energies ◽  
Ab Initio Study ◽  
Solvation Energies ◽  
Dipolar Aprotic Solvents ◽  
Complete Geometry Optimization

The paper deals with the solvation of Li+, Be2+, Na+, Mg2+, and Al3+ ions in dimethyl sulphoxide, dimethylformamide, acetonitrile, and water. The ab initio quantum chemical method was used to calculate the solvation energies, molecular structures, and charge distributions for the complexes water···ion, acetonitrile···ion, dimethyl sulphoxide···ion, and dimethylformamide···ion. The interaction energies were corrected for the superposition error. Complete geometry optimization was performed for the complex water···ion. Some generalizations are made on the basis of the results obtained.

scholarly journals Large Stabilization Effects by Intramolecular Beryllium Bonds in Ortho-Benzene Derivatives

Molecules ◽  
2021 ◽  
Vol 26 (11) ◽  
pp. 3401
Author(s):  
Tsai I-Ting ◽  
M. Merced Montero-Campillo ◽  
Ibon Alkorta ◽  
José Elguero ◽  
Manuel Yáñez
Keyword(s):  
Reaction Scheme ◽  
Binding Energies ◽  
Intramolecular Interactions ◽  
Isodesmic Reaction ◽  
Bond Critical Point ◽  
Interaction Energies ◽  
Benzene Derivatives ◽  
Covalent Interaction ◽  
Beryllium Bond ◽  
Donor And Acceptor

Intramolecular interactions are shown to be key for favoring a given structure in systems with a variety of conformers. In ortho-substituted benzene derivatives including a beryllium moiety, beryllium bonds provide very large stabilizations with respect to non-bound conformers and enthalpy differences above one hundred kJ·mol−1 are found in the most favorable cases, especially if the newly formed rings are five or six-membered heterocycles. These values are in general significantly larger than hydrogen bonds in 1,2-dihidroxybenzene. Conformers stabilized by a beryllium bond exhibit the typical features of this non-covalent interaction, such as the presence of a bond critical point according to the topology of the electron density, positive Laplacian values, significant geometrical distortions and strong interaction energies between the donor and acceptor quantified by using the Natural Bond Orbital approach. An isodesmic reaction scheme is used as a tool to measure the strength of the beryllium bond in these systems in terms of isodesmic energies (analogous to binding energies), interaction energies and deformation energies. This approach shows that a huge amount of energy is spent on deforming the donor–acceptor pairs to form the new rings.

scholarly journals TEM 3-beam study of annealing effects in InGaNAs using ab-initio structure factors for strain-relaxed supercells

2011 ◽  
Vol 326 ◽  
pp. 012026 ◽  
Author(s):  
K Müller ◽  
M Schowalter ◽  
O Rubel ◽  
D Z Hu ◽  
D M Schaadt ◽  
...  
Keyword(s):  
Ab Initio ◽  
Structure Factors ◽  
Annealing Effects ◽  
Ab Initio Structure
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