Efficient Ab Initio Estimation of Formation Enthalpies for Organic Compounds: Extension to Sulfur and Critical Evaluation of Experimental Data

2021 ◽  
Vol 125 (36) ◽  
pp. 8116-8131
Author(s):  
Eugene Paulechka ◽  
Andrei Kazakov
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Organic Compounds ◽  
Critical Evaluation ◽  
Formation Enthalpies

Ab-Initio Molecular Dynamics of Organic Compounds on a Massively Parallel Computer

1995 ◽  
Vol 408 ◽  
Author(s):  
François Gygi
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Ab Initio ◽  
Molecular Dynamics Simulations ◽  
Organic Compounds ◽  
Organic Molecules ◽  
Curvilinear Coordinates ◽  
Parallel Computer ◽  
Massively Parallel ◽  
Dynamics Simulations

AbstractWe present results of ab-initio electronic structure calculations and molecular dynamics simulations of organic molecules carried out using adaptive curvilinear coordinates, within the local density approximation of density functional theory. This approach allows for an accurate treatment of first-row elements, which makes it particularly suitable for investigations of organic compounds. A recent formulation of this method relies on a real-space approach which combines the advantages of finite-difference methods with the accuracy of adaptive coordinates, and is well suited for implementation on massively parallel computers. We used molecular dynamics simulations to obtain the fully relaxed structures of nitrosyl fluoride (FNO), and of the aromatic heterocycles furan and pyrrole. The equilibrium geometries obtained show excellent agreement with experimental data. The harmonic vibrational frequencies of furan and pyrrole were calculated by diagonalization of their dynamical matrix and are found to agree with experimental data within an rms error of 25 cm-1 and 28 cm-1 for furan and pyrrole respectively. This accuracy is comparable to that attained for smaller organic molecules using elaborate quantum chemistry methods.

scholarly journals Ab initio and CALPHAD-type thermodynamic investigation of the Ti-Al-Zr system

2019 ◽  
Vol 55 (3) ◽  
pp. 427-437 ◽  
Author(s):  
Z.-X. Deng ◽  
D.-P. Zhao ◽  
Y.-Y. Huang ◽  
L.-L. Chen ◽  
H. Zou ◽  
...  
Keyword(s):  
Experimental Data ◽  
Phase Equilibria ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Thermodynamic Parameters ◽  
Vertical Section ◽  
Calphad Approach ◽  
Alloying Element ◽  
Formation Enthalpies ◽  
End Members

Ti?Al based alloys have been widely used in the aeronautics and aerospace. Adding alloying element Zr can significantly improve their high-temperature endurance and corrosion resistance. To investigate the influence of the addition of element Zr on the properties of the Ti?Al system, ab initio calculations and the CALPHAD (CALculation of PHAse Diagrams) method were used to evaluate the Ti?Al?Zr ternary system. Ab initio calculations were carried out to calculate the formation enthalpies of intermetallic compounds and end-members. CALPHAD approach was employed to optimize the thermodynamic parameters based on experiments. The experimental data of phase equilibria at 1073, 1273, 1473, and 1573 K, as well as a vertical section of the Ti3Al?Ti + 5 wt.% Zr were used to assess this system. The thermodynamic parameters of the binary Ti?Al, Al?Zr and Ti?Zr systems were acquired from recent assessments, and the ternary ones were evaluated in the present work. The Ti?Al?Zr ternary dataset has been established and the calculated results are in close agreement with the experimental data on both thermodynamics and phase equilibria.

Modeling of experimental data on trace elements and organic compounds content in industrial waste dumps

Chemosphere ◽  
2016 ◽  
Vol 162 ◽  
pp. 189-198 ◽  
Author(s):  
Adam Smoliński ◽  
Leszek Drobek ◽  
Václav Dombek ◽  
Andrzej Bąk
Keyword(s):  
Experimental Data ◽  
Trace Elements ◽  
Organic Compounds ◽  
Industrial Waste ◽  
Waste Dumps

scholarly journals THE METHOD OF INCREMENTS — A WAVEFUNCTION-BASED AB-INITIO CORRELATION METHOD FOR SOLIDS

2007 ◽  
Vol 21 (13n14) ◽  
pp. 2204-2214 ◽  
Author(s):  
BEATE PAULUS
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Ground State ◽  
Infinite System ◽  
Correlation Energy ◽  
Correlation Method ◽  
Many Body ◽  
Hartree Fock ◽  
The Many ◽  
Good Agreement

The method of increments is a wavefunction-based ab initio correlation method for solids, which explicitly calculates the many-body wavefunction of the system. After a Hartree-Fock treatment of the infinite system the correlation energy of the solid is expanded in terms of localised orbitals or of a group of localised orbitals. The method of increments has been applied to a great variety of materials with a band gap, but in this paper the extension to metals is described. The application to solid mercury is presented, where we achieve very good agreement of the calculated ground-state properties with the experimental data.

Calculating Fundamental Vibrational Frequencies of Rutile by Combining Ab Initio Method with GF Matrix Method

1994 ◽  
Vol 05 (02) ◽  
pp. 299-301
Author(s):  
Lin Libin ◽  
Zheng Xiangyin
Keyword(s):  
Experimental Data ◽  
Ab Initio ◽  
Matrix Method ◽  
Cluster Model ◽  
Normal Modes ◽  
Vibrational Frequencies ◽  
Ab Initio Method ◽  
Environment Factor ◽  
Factor Α ◽  
Good Agreement

Based on cluster model, we have calculated the fundamental vibrational frequencies of rutile by combining ab initio method and Wilson’s GF-matrix method. In the calculation, we have introduced the concept of environment factor α to correct the force field of the cluster model. The results of calculation are in good agreement to the experimental data and the normal modes give us clear physical picture of the crystal vibration.

Contributions to Silicon-Hydrogen Bond-Stretching Frequency in Amorphous Si Alloys

1992 ◽  
Vol 258 ◽  
Author(s):  
Z. Jing ◽  
J. L. Whitten ◽  
G. Lucovsky
Keyword(s):  
Experimental Data ◽  
Hydrogen Bond ◽  
Dielectric Constant ◽  
Ab Initio ◽  
Effective Dielectric Constant ◽  
Bond Energies ◽  
Calculated Frequency ◽  
Bond Stretching ◽  
Amorphous Si ◽  
Good Agreement

ABSTRACTWe have performed ab initio calculations and determined the bond-energies and vibrational frequencies of Si-H groups that are: i) attached to Si-atoms as their immediate, and also more distant neighbors; and ii) attached to three O-atoms as their immediate neighbors, but are connected to an all Si-atom matrix. These arrangements simulate bonding geometries on Si surfaces, and the calculated frequency for i) is in good agreement with that of an Si-H group on an Si surface. To compare these results with a-Si:H alloys it is necessary to take into account an additional factor: the effective dielectric constant of the host. We show how to do this, demonstrating the way results of the ab initio calculations should then be compared with experimental data.

Application of biological activated carbon anaerobic reactor for treatment of hazardous chemicals

2006 ◽  
Vol 53 (11) ◽  
pp. 251-260 ◽  
Author(s):  
H. Tsuno ◽  
M. Kawamura ◽  
T. Oya
Keyword(s):  
Experimental Data ◽  
Activated Carbon ◽  
Organic Compounds ◽  
Adsorptive Capacity ◽  
Biological Degradation ◽  
Hazardous Chemicals ◽  
High Concentration ◽  
Expanded Bed ◽  
Biological Activated Carbon ◽  
Anaerobic Reactor

An expanded-bed anaerobic reactor with granular activated carbon (GAC) medium has been developed to treat wastewaters that contain a high concentration of inhibitory and/or refractory organic compounds as well as readily degradable organic compounds. The process is characterised by a combination of two removal mechanisms; adsorption on GAC and biological degradation by microorganisms grown on GAC. Applicability of the reactor to treatment of phenol, chloroacetaldehyde (CAA), pentachlorophenol (PCP) and tetrachloroethylene (PCE) was discussed based on experimental data. All chemicals focused on here were removed well and stably at a removal efficiency of more than 98% even during starting operation and shock load operation. Chemicals in influent that exceeded biological degradation capacity was initially adsorbed on GAC and then gradually degraded, and hence the adsorptive capacity of GAC was regenerated biologically. These results proved that a biological activated carbon anaerobic reactor was effective for treatment of wastewater containing hazardous chemicals, especially for strongly absorbable chemicals, as well as readily degradable organic compounds at high concentration.

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