Interaction of Hydrogen Atoms with Vacancies and Divacancies in bcc Iron

2016 ◽  
Vol 870 ◽  
pp. 550-557 ◽  
Author(s):  
A.V. Verkhovykh ◽  
A.A. Mirzoev ◽  
G.E. Ruzanova ◽  
D.A. Mirzaev ◽  
K.Yu. Okishev
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Formation Energy ◽  
Equilibrium Concentration ◽  
Dft Method ◽  
Hydrogen Binding ◽  
Hydrogen Atoms ◽  
Single Vacancy ◽  
Bcc Iron ◽  
Hydrogen Interaction

The paper presents the results of both ab initio and thermodynamic analysis of vacancy and divacancy formation and hydrogen interaction with them in alpha (bcc) iron. Ab initio calculations were performed by DFT method using LAPW in WIEN2k package. Monovacancy formation energy was found to be 2.15 eV and divacancy binding energy 0.22 ± 0.01 eV. Equlibrium fraction of vacancies bound into divacancies is of the order of 10–5 even at the highest temperatures close to bcc → fcc transformation point. Hydrogen has a strong interaction with monovacancies (vacancy-hydrogen binding energy decreasing from 0.60 to 0.31 eV for the first–fifth H atom inside a single vacancy) but has only a small effect on divacancy formation energy that is equal to 0.28, 0.19 and 0.17 for the case of joining of VH + V, VH + VH and VH2 + VH2, respectively. This means that the presence of hydrogen cannot significantly increase the equilibrium concentration of divacancies.

Hydrogen adsorbed in ab initio computationally simulated nanoporous carbon. An energetics study

2007 ◽  
Vol 1042 ◽  
Author(s):  
R. M. Valladares ◽  
Alexander Valladares ◽  
A. G. Calles ◽  
Ariel A. Valladares
Keyword(s):  
Hydrogen Atom ◽  
Binding Energy ◽  
Total Energy ◽  
Ab Initio ◽  
Molecular Hydrogen ◽  
Molecular Form ◽  
Average Energy ◽  
Nanoporous Carbon ◽  
Hydrogen Atoms ◽  
Pure Carbon

AbstractNanoporous carbon has been considered an interesting and potentially useful material for storing hydrogen. Using nanoporous carbon periodic supercells with 216 atoms and 50 % porosity, constructed with a novel ab initio approach devised by us, the dangling bonds of the carbon atoms were first saturated with hydrogen, then relaxed and its total energy calculated with and without hydrogen. Next the same number of hydrogen atoms, in molecular form, was randomly placed within the pore of the pure carbon supercell, then the sample relaxed, and finally its total energy calculated, also with and without hydrogens. From these results the average energy per hydrogen atom is obtained for both cases. For the molecular hydrogen sample the binding energy found per hydrogen atom is 343.89 meV, which compares favourably with values reported in the literature, 300-400 meV/molecule.

Formation of surface layer of hydrogen in pure aluminum

2019 ◽  
Vol 484 (1) ◽  
pp. 56-60
Author(s):  
D. A. Indejtsev ◽  
E. V. Osipova
Keyword(s):  
Surface Layer ◽  
Hydrogen Atom ◽  
Ab Initio ◽  
Pure Aluminum ◽  
Hydrogen Atoms ◽  
Energy Characteristics ◽  
Aluminum Crystal

Hydrogen atom behavior in pure aluminum is described by ab initio modelling. All main energy characteristics of the system consisting of hydrogen atoms in a periodic aluminum crystal are found.

Ab Initio Determination of a New Complex Structure (55 Non-Hydrogen Atoms) from Synchrotron Powder Data: An Uncommon Nickel Succinate, Ni7(C4H4O4)4(OH)6(H2O)3•7H2O

2004 ◽  
Vol 443-444 ◽  
pp. 333-336
Author(s):  
N. Guillou ◽  
C. Livage ◽  
W. van Beek ◽  
G. Férey
Keyword(s):  
Ab Initio ◽  
Complex Structure ◽  
Three Dimensional ◽  
Free Water ◽  
Hydrogen Atoms ◽  
Monoclinic System ◽  
Synchrotron Powder Diffraction ◽  
Chloride Hexahydrate ◽  
Autogenous Pressure

Ni7(C4H4O4)4(OH)6(H2O)3. 7H2O, a new layered nickel(II) succinate, was prepared hydrothermally (180°C, 48 h, autogenous pressure) from a 1:1.5:4.1:120 mixture of nickel (II) chloride hexahydrate, succinic acid, potassium hydroxide and water. It crystallizes in the monoclinic system (space group P21/c, Z = 4) with the following parameters a = 7.8597(1) Å, b = 18.8154(3)Å, c = 23.4377(4) Å,ϐ = 92.0288(9)°, and V = 3463.9(2) Å3. Its structure, which contains 55 non-hydrogen atoms, was solved ab initio from synchrotron powder diffraction data. It can be described from hybrid organic-inorganic layers, constructed from nickel oxide corrugated chains. These chains are built up from NiO6hexameric units connected via a seventh octahedron. Half of the succinates decorate the chains, and the others connect them to form the layers. The three dimensional arrangement is ensured by hydrogen bonds directly between two adjacent layers and via free water molecules.

Hydrogenated Amorphous Silicon Nitride: Structural and Electronic Properties

1998 ◽  
Vol 538 ◽  
Author(s):  
J. F. Justo ◽  
F. De Brito Mota ◽  
A. Fazziom
Keyword(s):  
Silicon Nitride ◽  
Ab Initio ◽  
Amorphous Silicon ◽  
Electronic Properties ◽  
Interatomic Potential ◽  
Hydrogen Atoms ◽  
Hydrogen Incorporation ◽  
Amorphous Silicon Nitride ◽  
Structural And Electronic Properties ◽  
Hydrogenated Amorphous

AbstractWe combined empirical and ab initio methods to study structural and electronic properties of amorphous silicon nitride. For such study, we developed an interatomic potential to describe the interactions between silicon, nitrogen, and hydrogen atoms. Using this potential, we performed Monte Carlo simulations in a simulated annealing scheme to study structural properties of amorphous silicon nitride. Then this potential was used to generate relevant structures of a-SiNx:Hy which were input configurations to ab initio calculations. We investigated the electronic and structural role played by hydrogen incorporation in amorphous silicon nitride.

Quantum-Chemical Ab Initio Calculations on Inda- and Thallabenzene (C5H5In and C5H5Tl) and their Structural Isomers η5-C5H5In and η5-C5H5Tl

2018 ◽  
Vol 71 (3) ◽  
pp. 102
Author(s):  
Emma Persoon ◽  
Yuekui Wang ◽  
Gerhard Raabe
Keyword(s):  
Ab Initio ◽  
Quantum Chemical ◽  
Density Functional ◽  
Single Point ◽  
Normal Modes ◽  
Dft Method ◽  
Basis Sets ◽  
Triplet States ◽  
Structural Isomers ◽  
Td Dft

Quantum-chemical ab initio, time-independent, as well as time-dependent density functional theory (TD-DFT) calculations were performed on the so far elusive heterocycles inda- and thallabenzene (C5H5In and C5H5Tl), employing several different methods (MP2, CISD, CCSD, CCSD(T), BD, BD(T), QCISD, QCISD(T), CASSCF, DFT/B3LYP), effective core potentials, and different basis sets. While calculations on the MP2 level predict the ground states of the title compounds to be singlets with the first triplet states between 13 and 15 kcal mol−1 higher in energy, single point calculations with the QCISD(T), CCSD(T), and BD(T) methods at CCSD-optimized structures result in energy differences between the singlet and the triplet states in the range between 0.3 and 2.1 kcal mol−1 in favour of the triplet states. According to a CASSCF(8,8) calculation the triplets are also more stable by about 2.5–2.9 kcal mol−1. Calculations were also performed for the C5v-symmetric η5 structural isomers (cyclopentadienylindium, CpIn, and cyclopentadienylthallium, CpTl, Cp = C5H5) of the title compounds. At the highest level of theory employed in this study, C5H5In is between 79 and 88 kcal mol−1 higher in energy than CpIn, while this energy difference is even larger for thallabenzene where C5H5Tl is energetically between 94 and 102 kcal mol−1 above CpTl. In addition we report on the UV/vis spectra calculated with a TD-DFT method as well as on the spectra of the normal modes of C5H5In and C5H5Tl. Both types of spectra might facilitate identification of the title compounds eventually formed in photolysis or pyrolysis experiments.

scholarly journals Toward fully quantum modelling of ultrafast photodissociation imaging experiments. Treating tunnelling in the ab initio multiple cloning approach

2016 ◽  
Vol 194 ◽  
pp. 81-94 ◽  
Author(s):  
Dmitry V. Makhov ◽  
Todd J. Martinez ◽  
Dmitrii V. Shalashilin
Keyword(s):  
Kinetic Energy ◽  
Ab Initio ◽  
Energy Release ◽  
Kinetic Energy Release ◽  
Total Kinetic Energy ◽  
Recent Effort ◽  
Experimental Measurements ◽  
Quantum Level ◽  
Hydrogen Atoms ◽  
Quantum Simulations

We present an account of our recent effort to improve simulation of the photodissociation of small heteroaromatic molecules using the Ab Initio Multiple Cloning (AIMC) algorithm. The ultimate goal is to create a quantitative and converged technique for fully quantum simulations which treats both electrons and nuclei on a fully quantum level. We calculate and analyse the total kinetic energy release (TKER) spectra and Velocity Map Images (VMI), and compare the results directly with experimental measurements. In this work, we perform new extensive calculations using an improved AIMC algorithm that now takes into account the tunnelling of hydrogen atoms. This can play an extremely important role in photodissociation dynamics.

Ab initio study on hydrogen interaction with calcium decorated silicon carbide nanotube

2017 ◽  
Vol 42 (16) ◽  
pp. 11452-11460 ◽  
Author(s):  
Jessiel Siaron Gueriba ◽  
Allan Abraham Bustria Padama ◽  
Al Rey Villagracia ◽  
Melanie David ◽  
Nelson Arboleda ◽  
...  
Keyword(s):  
Silicon Carbide ◽  
Ab Initio ◽  
Ab Initio Study ◽  
Silicon Carbide Nanotube ◽  
Hydrogen Interaction

Ab Initio Study of the Structure, Binding Energy, and Vibrations of the HOCl-H2O Complex

1995 ◽  
Vol 99 (7) ◽  
pp. 1919-1922 ◽  
Author(s):  
Theodore S. Dibble ◽  
Joseph S. Francisco
Keyword(s):  
Binding Energy ◽  
Ab Initio ◽  
Ab Initio Study

BINDING ENERGY OF HYDROGEN TO MIXED AND SCREW DISLOCATION

2005 ◽  
Vol 12 (02) ◽  
pp. 227-232 ◽  
Author(s):  
S. B. GESARI ◽  
B. L. IRIGOYEN ◽  
A. JUAN
Keyword(s):  
Crystal Structure ◽  
Experimental Data ◽  
Binding Energy ◽  
Dominant Role ◽  
Dislocation Core ◽  
Electron Delocalization ◽  
The Core ◽  
Mixed Dislocation ◽  
Overlap Population ◽  
Bcc Iron

We have studied the effect of hydrogen on the cohesion of two types of dislocation in bcc iron at an atomistic level, using the atom superposition and electron delocalization molecular orbital (ASED-MO) method. The most stable positions for one hydrogen at each dislocation core were determined. It was found that the total energy of the cluster decreases when the hydrogen is located at the core. This effect is higher in a mixed dislocation in accordance with the experimental data. The computed results show that hydrogen is a strong embrittler and that a decrease in the Fe–Fe overlap population plays a dominant role in the decohesion of the crystal structure.

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