A Generalized Model for the Analysis of Groundwater Radiolysis

1984 ◽  
Vol 44 ◽  
Author(s):  
Stephen L. Nicolosi
Keyword(s):  
Experimental Data ◽  
Basis Set ◽  
Generalized Model

AbstractA generalized groundwater radiolysis model which is under development at Battelle-Columbus is described. This model uses a 55 reaction basis set for the radiolysis of the solvent. The basis set of reactions was chosen from the literature after comparing several descriptions against experimental data. This basis set has been augmented with 17 additional reactions to allow the description of the radiolysis of groundwater containing iron. The development of this mechanism is described, and comparisons with experimental data are shown.

Study of potential curves by UHF type methods. CH4 molecule and its dissociation products

1986 ◽  
Vol 51 (4) ◽  
pp. 731-737
Author(s):  
Viliam Klimo ◽  
Jozef Tiňo
Keyword(s):  
Experimental Data ◽  
Quantum Chemistry ◽  
High Energy ◽  
Basis Set ◽  
Electronic Correlation ◽  
Exact Methods ◽  
Energy Parameters ◽  
Bond Functions ◽  
The Individual ◽  
Potential Curves

Geometry and energy parameters of the individual dissociation intermediate steps of CH4 molecule, parameters of the barrier to linearity and singlet-triplet separation of the CH2 molecule have been calculated by means of the UMP method in the minimum basis set augmented with the bond functions. The results agree well with experimental data except for the geometry of CH2(1A1) and relatively high energy values of CH(2II) and CH2(1A1) where the existence of two UHF solutions indicates a necessity of description of the electronic correlation by more exact methods of quantum chemistry.

Comparison of the Conformational Stability for Several Vinylhalomethanes and Silanes with Experiment Using MP2 Perturbation Theory and DFT

2007 ◽  
Vol 72 (1) ◽  
pp. 15-50 ◽  
Author(s):  
Wolfgang Förner ◽  
Hassan M. Badawi
Keyword(s):  
Experimental Data ◽  
Vibrational Spectra ◽  
Recent Literature ◽  
Conformational Stability ◽  
Basis Set ◽  
Major Conclusion ◽  
Stable Conformer ◽  
Polarization Functions ◽  
Complete Series ◽  
Triple Zeta

In recent literature it was reported that the valence triple zeta basis set augmented by polarization functions is not too reliable for vinyl monohalo- and dihalomethanes and -silanes, the halogen being fluorine and chlorine. The major conclusion was that a valence triple zeta basis is too small to be augmented by polarization functions in a balanced way, at least on vinylmonofluoromethane. Thus we decided to apply the 6-311++G** basis set to the complete series of methanes, silanes and germanes (the latter ones are just added for completeness because no experimental data are available for them and, moreover, we published them already previously) and to compare the results to experimental data available in the literature to see whether the failures of this basis set show up in the complete series of molecules. In the literature we found five such molecules and the information which of the conformers is the most stable. Indeed we found that predictions on the relative stability of conformers in those systems with this basis set and MP2 as well as DFT are with a 60:40 chance, three being correct predictions and two being incorrect ones out of the five. However, since the energy differences are rather small in these systems and due to the fact that - as a consequence of twofold degeneracy of the gauche conformer on the potential curve of the torsional vibration - the abundances of the conformers in equilibrium do not change too much, we decided to calculate also vibrational spectra for three examples and to compare them also to experiment. It is reported that besides the failures in total energy (we have chosen two examples where predictions of the nature of the stable conformer are correct, and one where it is not), the vibrational spectra are rather well reproduced, especially when experimental energies are used to calculate abundances in equilibrium in the case where the prediction of the stable conformer failed.

Systematic ab initio study of the compressibility of silicate garnets

2001 ◽  
Vol 57 (2) ◽  
pp. 163-177 ◽  
Author(s):  
V. Milman ◽  
E. V. Akhmatskaya ◽  
R. H. Nobes ◽  
B. Winkler ◽  
C. J. Pickard ◽  
...  
Keyword(s):  
Experimental Data ◽  
Density Functional ◽  
Structural Parameters ◽  
Applied Pressure ◽  
Basis Set ◽  
Ionic Radii ◽  
Cell Parameters ◽  
The Density Functional Theory ◽  
Dodecahedral Site ◽  
Compression Mechanism

The structural properties of the silicate garnets andradite, Ca3Fe2Si3O12, uvarovite, Ca3Cr2Si3O12, knorringite, Mg3Cr2Si3O12, goldmanite, Ca3V2Si3O12, blythite, Mn^{2+}_3Mn^{3+}_2Si3O12, skiagite, Fe^{2+}_3Fe^{3+}_2Si3O12, calderite, Mn^{2+}_3Fe^{3+}_2Si3O12, and khoharite, Mg3Fe^{3+}_2Si3O12, have been investigated with a quantum-mechanical model as a function of applied pressure. The study has been performed with the density functional theory code CASTEP, which uses pseudopotentials and a plane-wave basis set. All structural parameters have been optimized. The calculated static geometries (cell parameters, internal coordinates of atoms and bond lengths), bulk moduli and their pressure derivatives are in good agreement with the experimental data available. Predictions are made for those cases where no experimental data have been reported. The data clearly indicate that the elastic properties of all silicate garnets are dominated by the compressibility of the dodecahedral site. The compression mechanism is found to be based on a bending of the angle between the centers of the SiO4 tetrahedra and the adjacent octahedra, as in the aluminosilicate garnets. An analysis of the relationship between ionic radii of the cations and the compressibility of silicate garnets is presented.

Conformational Structure of Chloromethyldichlorophosphines

2002 ◽  
Vol 57 (6-7) ◽  
pp. 333-336
Author(s):  
Evgenii A. Romanenko ◽  
Alexander M. Nesterenko
Keyword(s):  
Experimental Data ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Electron Correlation ◽  
Basis Set ◽  
Conformational Structure ◽  
Gauche Conformation ◽  
Nuclear Quadrupole ◽  
Set Up ◽  
Good Agreement

IThe 35Cl nuclear quadrupole resonances (77 K) and ab initio calculations of trichloromethyldichlorophosphine () show that it exists in the chess conformation form. The barrier to internal rotation about the P-C bond in I at the RHF/6-31++ G(d,p) level equals to 38.1 kJ mol-1. In chloromethyldichlorophosphine (II) the extension of the basis set up to the RHF/6-311++G(df, pd) level does not improve the description of the most preferable gauche-conformation; only if electron correlation (at the MP2 level) is taken into account the results are in a good agreement with experimental data.

The structure and energetics of low-lying states of RCO and RNN free radicals

1977 ◽  
Vol 55 (5) ◽  
pp. 863-868 ◽  
Author(s):  
N. Colin Baird ◽  
Harish B. Kathpal
Keyword(s):  
Experimental Data ◽  
Free Radicals ◽  
Hydrogen Atom ◽  
Ab Initio ◽  
Open Shell ◽  
Basis Set ◽  
Basis Sets ◽  
Mo Calculations ◽  
Decomposition Products ◽  
Ab Initio Mo Calculations

The important geometrical variables in the structures of the lowest 2A′ and 2A′′ states of the free radicals HCO, CH3CO, NH2CO, HNN, and CH3NN have been determined by ab initio MO calculations using the STO-3G basis set. The energy differences between the states, and the energies of the radicals relative to their decomposition products and relative to their hydrogen atom addition products, are reported using both STO-3G and 4-31G basis sets in the restricted open-shell calculations. The trends in these results and their relation to available experimental data are discussed.

scholarly journals GEOMETRICAL AND ELECTRONIC STRUCTURE OF PROPYL-, TETRAMETHYL-, DIMETHYLETHYL- AND BUTYLADAMANTANES AND THEIR THERMODYNAMIC CHARACTERISTIC ACCORDING TO DFT

2018 ◽  
Vol 61 (12) ◽  
pp. 108-114
Author(s):  
Amanzhan T. Saginayev ◽  
Evgenii I. Bagrii
Keyword(s):  
Experimental Data ◽  
Qualitative Agreement ◽  
Isopropyl Alcohol ◽  
Analytical Calculation ◽  
Dft Method ◽  
Energy Functional ◽  
Basis Set ◽  
Stationary Points ◽  
Important Conclusion ◽  
Good Agreement

Propyladamantanes were synthesized by alkylation of adamantane with isopropyl alcohol in the temperature range from 5 to 40 °C in the presence of 96% sulfuric acid. Tetramethyl- and dimethylethyladamantanes were synthesized by isomerization of perhydroanthracene in the presence of aluminium oxide catalyst on the setup of the flow type. Isomers of butyladamantanes were obtained by the reaction of alkylation of the adamantane with isooctane. For each molecule, the optimization of the geometric parameters of atoms was carried out using analytical calculation methods. By calculating the frequencies of normal vibrations using the second derivatives, it was confirmed that the stationary points determined by optimizing the geometry correspond to the minima of the potential energy surface. The structure of 1-n-propyladamantane (I), 1-isopropyl-adamantane (II), 2-n-propyladamantane (III), 1,2-di-n-propyladamantane (IV), 1,3-dimethyl-5-ethyladamantane (V), 1,3,5,6-tetramethyladamantane (VI), 1,3,5,7-tetramethyladamantane (VII), perhydroanthracene (VIII), 1-n-butyladamantane (IX), 1-isobutyladamantane (X), 1-sec-butyladamantane (XI) has been studied using the DFT method with the Becke–Lee–Yang–Parr hybrid energy functional of electron density with the 6-31G* basis set. The geometric and electronic characteristics of the compounds and their total energy, normal vibration frequencies have been calculated. It has been shown that the calculated Gibbs free energies of formation for the perhydroanthracene isomerization products are in qualitative agreement with the experimental product composition of the isomerate and alkylation of adamantane with isopropyl alcohol are in qualitative agreement with the experimental composition of the products. A good agreement of calculated and experimental data on the composition of equilibrium mixtures was obtained. The theoretical geometry of the synthesized alkyladamantanes with Td symmetry very well agrees with the results of electron diffraction. Closest to the results obtained experimentally, the geometry was predicted by B3LYP, in which the lengths of C-C and C-H bonds are close to 1.544 and 1,100Ả, respectively, and the C-Csec-C and C-Cter-C angles are 109°. The results of the calculation using the B3LYP method are in good agreement with the experimental data. There is no definite relationship between the size of the molecules and the convergence of the calculated and experimental data. A practically important conclusion arising from the results of this and previous studies is that the use of the calculation method leads to “chemically accurate” data.  

The ab initio Calculation of Nuclear Quadrupole Coupling Constants with Special Reference to 33S

1992 ◽  
Vol 47 (1-2) ◽  
pp. 203-216 ◽  
Author(s):  
Michael H. Palmer
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ab Initio Calculation ◽  
Coupling Constants ◽  
Basis Set ◽  
Equilibrium Geometry ◽  
Relaxation Methods ◽  
Quadrupole Coupling ◽  
Nuclear Quadrupole ◽  
The Relationship

AbstractThe ab initio calculation of 33S nuclear quadrupole coupling constants (NQCC) for a range of S-containing compounds with S2, S4 and S6 bonding types is described. All of the calculations used a triple zeta valence + polarisation basis set (TZVP) of gaussian type orbitals; all of the molecules were studied at the TZVP equilibrium geometry. The electric field gradients (EFG) calculated were correlated with the experimental NQCC obtained by either microwave spectroscopy (MW), nuclear quadrupole resonance (NQR) or NMR relaxation methods; although the experimental data cover a wide diversity of chemical types over a long period of time, the slope of the relationship between the EFG (qii) and the NQCC (χii) yields a value for the 33S atomic quadrupole moment of - 0.064 barn, very close to recent calculations with a large atomic basis set, and to experimental data. The relationship between the EFG tensor components and the internal molecular structure features is discussed for a diverse series of molecules.

Structures, binding energies, and thermodynamic functions of NH4+, NH3•+, and their H2O complexes

1993 ◽  
Vol 71 (9) ◽  
pp. 1368-1377 ◽  
Author(s):  
David A. Armstrong ◽  
Arvi Rauk ◽  
Dake Yu
Keyword(s):  
Experimental Data ◽  
Gas Phase ◽  
Thermodynamic Functions ◽  
Hydration Shell ◽  
Binding Energies ◽  
Basis Set ◽  
Free Energies ◽  
Hydrated Complexes ◽  
Optimized Geometries ◽  
First Hydration Shell

Ab initio calculations are performed for [Formula: see text] and [Formula: see text] complexes for n = 0–5. For n = 0 and 1, the geometries of the complexes are optimized at the HF/6-31 + G* and MP2/6-31 + G* levels, and the energies are evaluated at the G2 level. For n = 2–5, the geometry optimizations and frequency calculations are carried out at the HF/6-31 + G* level, and the MP2/6-31 + G* energies are calculated at the HF optimized geometries. Basis set superposition errors are corrected by the Boys–Bernardi scheme at the HF/6-31 + G* level. The gas phase thermodynamic properties [Formula: see text] are evaluated as functions of temperature using standard statistical methods. Based on the calculated binding energies and the thermodynamic functions, the incremental changes in enthalpies and free energies, ΔHn and ΔGn, for the gas phase equilibria (H2O)n−1 M+ + H2O → (H2O)nM+ for M+ = NH4+ and NH3•+, are evaluated in comparison with the experimental data for [Formula: see text] the present results suggest conformations for the hydrated complexes observed in the experiments. The total free energy change for filling the first hydration shell is significantly more negative for NH3•+ than for NH4+.

Study on the Characteristics of Sediment Incipient Motion in Pressure Pipeline

2014 ◽  
Vol 1010-1012 ◽  
pp. 1028-1032
Author(s):  
Ming Hui Lei ◽  
Rui Hua Nie ◽  
Su Qin Yuan ◽  
Xing Nian Liu
Keyword(s):  
Experimental Data ◽  
Velocity Distribution ◽  
Critical Velocity ◽  
Incipient Motion ◽  
Generalized Model ◽  
Model Experiments ◽  
Pressure Pipeline ◽  
Recorded Data ◽  
Sediment Incipient Motion

The generalized model experiments were designed and conducted in the pressure pipeline to investigate the characteristic of sediment incipient motion. There were some differences between the measured sediment critical velocity and the predictive one which was calculated by traditional formulas. In this paper, the analyses of velocity distribution and its corresponding effect on the sediment incipient motion in the pressure pipeline are done. Then, a simple but available formula which is suitable for the prediction of sediment critical velocity in the pressure pipeline is proposed. Finally, this formula is verified by experimental data and good agreements are observed between the recorded data and predictions.

Model Test Research on Soil-Landslide Surge by River Channel Reservoir

2013 ◽  
Vol 353-356 ◽  
pp. 2610-2613
Author(s):  
Li Chen ◽  
Ping Yi Wang ◽  
Tao Yu ◽  
Fan Zhang ◽  
Yong Qiang Men
Keyword(s):  
Experimental Data ◽  
Influencing Factors ◽  
Model Test ◽  
Empirical Formula ◽  
Exchange Process ◽  
River Channel ◽  
Test Results ◽  
Generalized Model ◽  
Landslide Occurrence

By fully collected and surveyed on the soil landslide, with the help of generalized model, the experiment simulated the landslide occurrence and exchange process of soil landslide entered the water. Through the calculation and analysis of test results and influencing factors, it is given out the height of the initial surge, variation of the progressive surge and empirical formula of soil-landslide surge. Compared with experimental data, it is found that empirical formula has certain accuracy and it can provide a certain reference on surge disaster forecast.

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