scholarly journals Nitrogen Dissolution in Liquid Ga and Fe: Comprehensive Ab Initio Analysis, Relevance for Crystallization of GaN

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1306
Author(s):  
Jacek Piechota ◽  
Stanislaw Krukowski ◽  
Petro Sadovyi ◽  
Bohdan Sadovyi ◽  
Sylwester Porowski ◽  
...  
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Chemical Potential ◽  
Nitrogen Solubility ◽  
Molecular Nitrogen ◽  
Ideal Gas ◽  
The Difference ◽  
Good Agreement

The dissolution of molecular nitrogen in Ga and Fe was investigated by ab initio calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between Ga4s and Ga4p and N2p states whereas for Fe this is by N2p to Fe4s, Fe4p and Fe3d states. Accordingly, the energy of dissolution of N2 for arbitrarily chosen starting atomic configurations was 0.535 eV/mol and −0.299 eV/mol for Ga and Fe, respectively. For configurations optimized with molecular dynamics, the difference between the corresponding energy values, 1.107 eV/mol and 0.003 eV/mol, was similarly large. Full thermodynamic analysis of chemical potential was made employing entropy-derived terms in a Debye picture. The entropy-dependent terms were obtained via a normal conditions path to avoid singularity of ideal gas entropy at zero K. Nitrogen solubility as a function of temperature and N2 pressure was evaluated, being much higher for Fe than for Ga. For T=1800 K and p=104 bar, the N concentration in Ga was 3×10−3 at. fr. whereas for Fe, it was 9×10−2 at. fr. in very good agreement with experimental data. It indicates that liquid Fe could be a prospective solvent for GaN crystallization from metallic solutions.

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.

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.

Dose-window dependence on Si crystal orientation in separation by implanted oxygen substrate formation

2004 ◽  
Vol 19 (12) ◽  
pp. 3607-3613 ◽  
Author(s):  
H. Iikawa ◽  
M. Nakao ◽  
K. Izumi
Keyword(s):  
Experimental Data ◽  
Numerical Analysis ◽  
Crystal Orientation ◽  
Oxygen Ion ◽  
The Difference ◽  
First Time ◽  
Good Agreement

Separation by implemented oxygen (SIMOX)(111) substrates have been formed by oxygen-ion (16O+) implantation into Si(111), showing that a so-called “dose-window” at 16O+-implantation into Si differs from Si(100) to Si(111). In SIMOX(100), an oxygen dose of 4 × 1017/cm2 into Si(100) is widely recognized as the dose-window when the acceleration energy is 180 keV. For the first time, our work shows that an oxygen dose of 5 × 1017/cm2 into Si(111) is the dose-window for the formation of SIMOX(111) substrates when the acceleration energy is 180 keV. The difference between dose-windows is caused by anisotropy of the crystal orientation during growth of the faceted buried SiO2. We also numerically analyzed the data at different oxidation velocities for each facet of the polyhedral SiO2 islands. Numerical analysis results show good agreement 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.

Hydrogen Storage in MgH2 Matrices: An Ab-Initio Study of Mg-MgH2 Interface

2008 ◽  
Vol 139 ◽  
pp. 23-28 ◽  
Author(s):  
Simone Giusepponi ◽  
Massimo Celino ◽  
Fabrizio Cleri ◽  
Amelia Montone
Keyword(s):  
Molecular Dynamics ◽  
Total Energy ◽  
Ab Initio ◽  
Atomic Hydrogen ◽  
Level Structure ◽  
Atomic Level ◽  
Work Of Adhesion ◽  
Ab Initio Study ◽  
Dynamics Method ◽  
Good Agreement

We studied the atomic-level structure of a model Mg-MgH2 interface by means of the Car-Parrinello molecular dynamics method (CPMD). The interface was characterized in terms of total energy calculations, and an estimate of the work of adhesion was given, in good agreement with experimental results on similar systems. Furthermore, the interface was studied in a range of temperatures of interest for the desorption of hydrogen. We determined the diffusivity of atomic hydrogen as a function of the temperature, and give an estimate of the desorption temperature.

scholarly journals Three-nucleon forces

2014 ◽  
Vol 23 (09) ◽  
pp. 1430015 ◽  
Author(s):  
Peter U. Sauer
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Body Problem ◽  
Many Body ◽  
Nuclear Systems ◽  
The Difference

In this paper, the role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries toward calculationally converged results. Genuine forces make up the Hamiltonian. They represent the chosen underlying dynamics. The hierarchy of contributions arising from genuine two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the description of some observables. Their contributions to observables are small on the scale set by two-nucleon forces.

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