H2 in solid C60: Coupled translation-rotation eigenstates in the octahedral interstitial site from quantum five-dimensional calculations

2013 ◽  
Vol 138 (24) ◽  
pp. 244707 ◽  
Author(s):  
Shufeng Ye ◽  
Minzhong Xu ◽  
Stephen FitzGerald ◽  
Kirill Tchernyshyov ◽  
Zlatko Bačić
Keyword(s):  
Interstitial Site ◽  
Octahedral Interstitial Site

Magnetic Volume Effect of Hydrogen Diffusion in Palladium

2020 ◽  
Vol 310 ◽  
pp. 29-33
Author(s):  
Sarantuya Nasantogtokh ◽  
Xin Cui ◽  
Zhi Ping Wang
Keyword(s):  
Transition Metal ◽  
Density Of States ◽  
Density Functional ◽  
Hydrogen Diffusion ◽  
Magnetic Moments ◽  
Interstitial Site ◽  
Volume Effect ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Octahedral Interstitial Site

The electronic and magnetic properties of palladium hydrogen are investigated using first-principles spin-polarized density functional theory. By studying the magnetic moments and electronic structures of hydrogen atoms diffusing in face-centered cubic structure of transition metal Pd, we found that the results of magnetic moments are exactly the same in the two direct octahedral interstitial site-octahedral interstitial site diffusion paths-i.e. the magnetic moments are the largest in the octahedral interstitial site, and the magnetic moments are the lowest in saddle point positions. We also studied on the density of states of some special points, with the result that the density of states near the Fermi level is mainly contributed by 4d electrons of Pd and the change of magnetic moments with the cell volume in the unit cell of transition metal Pd with a hydrogen atom.

Effect of Boron and Hydrogen on the Electronic Structure of Ni3Al

1993 ◽  
Vol 319 ◽  
Author(s):  
N. Kioussis ◽  
H. Watanabe ◽  
R.G. Hemker ◽  
W. Gourdin ◽  
A. Gonis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Charge Density ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Interstitial Region ◽  
Ordered Intermetallic ◽  
Lmto Method ◽  
Structure Calculations

AbstractUsing first-principles electronic structure calculations based on the Linear-Muffin-Tin Orbital (LMTO) method, we have investigated the effects of interstitial boron and hydrogen on the electronic structure of the L12 ordered intermetallic Ni3A1. When it occupies an octahedral interstitial site entirely coordinated by six Ni atoms, we find that boron enhances the charge distribution found in the strongly-bound “pure” Ni3AI crystal: Charge is depleted at Ni and Al sites and enhanced in interstitial region. Substitution of Al atoms for two of the Ni atoms coordinating the boron, however, reduces the interstitial charge density between certain atomic planes. In contrast to boron, hydrogen appears to deplete the interstitial charge, even when fully coordinated by Ni atoms. We suggest that these results are broadly consistent with the notion of boron as a cohesion enhancer and hydrogen as an embrittler.

scholarly journals First-Principles Investigation of Atomic Hydrogen Adsorption and Diffusion on/into Mo-doped Nb (100) Surface

2018 ◽  
Vol 8 (12) ◽  
pp. 2466 ◽  
Author(s):  
Yang Wu ◽  
Zhongmin Wang ◽  
Dianhui Wang ◽  
Jiayao Qin ◽  
Zhenzhen Wan ◽  
...  
Keyword(s):  
First Principles ◽  
Atomic Hydrogen ◽  
Energy Barrier ◽  
Hydrogen Adsorption ◽  
Hydrogen Permeation ◽  
Diffusion Path ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Tetrahedral Interstitial Site ◽  
And Diffusion

To investigate Mo doping effects on the hydrogen permeation performance of Nb membranes, we study the most likely process of atomic hydrogen adsorption and diffusion on/into Mo-doped Nb (100) surface/subsurface (in the Nb12Mo4 case) via first-principles calculations. Our results reveal that the (100) surface is the most stable Mo-doped Nb surface with the smallest surface energy (2.75 J/m2). Hollow sites (HSs) in the Mo-doped Nb (100) surface are H-adsorption-favorable mainly due to their large adsorption energy (−4.27 eV), and the H-diffusion path should preferentially be HS→TIS (tetrahedral interstitial site) over HS→OIS (octahedral interstitial site) because of the correspondingly lower H-diffusion energy barrier. With respect to a pure Nb (100) surface, the Mo-doped Nb (100) surface has a smaller energy barrier along the HS→TIS pathway (0.31 eV).

Lithium and boron as interstitial palladium dopants for catalytic partial hydrogenation of acetylene

2017 ◽  
Vol 53 (3) ◽  
pp. 601-604 ◽  
Author(s):  
Ieuan T. Ellis ◽  
Elisabeth H. Wolf ◽  
Glenn Jones ◽  
Ben Lo ◽  
Molly Meng-Jung Li ◽  
...  
Keyword(s):  
Metal Nanoparticles ◽  
Electronic Properties ◽  
Interstitial Site ◽  
Partial Hydrogenation ◽  
Light Elements ◽  
Octahedral Interstitial Site

It is demonstrated that light elements, including lithium and boron atoms, can take residence in the octahedral (interstitial) site of a Pd lattice by modifying the electronic properties of the metal nanoparticles, and hence the adsorptive strength of a reactant.

Effects of boron on the mechanical properties of the TiAl–Ti3Al alloy: A first-principles investigation

2017 ◽  
Vol 31 (02) ◽  
pp. 1750002
Author(s):  
Zhong-Zhu Li ◽  
Ye Wei ◽  
Hong-Bo Zhou ◽  
Guang-Hong Lu
Keyword(s):  
Mechanical Properties ◽  
First Principles ◽  
Phase Interface ◽  
Interstitial Site ◽  
Site Preference ◽  
Al Alloy ◽  
Octahedral Interstitial Site ◽  
Binary Phase ◽  
Negative Effect ◽  
Energy Formula

Employing a first-principles method in combination with the empirical criterions, we have investigated the site preference of boron (B) and its effect on the mechanical properties of the binary-phase TiAl–Ti3Al alloy. It is found that B energetically prefers to occupy the Ti-rich octahedral interstitial site, because B is more favorable to bond with Ti in comparison with Al. The occupancy tendency of B in the TiAl–Ti3Al alloy is the TiAl/Ti3Al interface [Formula: see text] Ti3Al [Formula: see text] TiAl, thus B tends to segregate into the binary-phase interface in the TiAl–Ti3Al alloy. The charge density difference shows that B at the TiAl–Ti3Al interface will form strong B–Ti bonds and weak B–Al bonds, leading to the significant increasing of the cleavage energy [Formula: see text] and the unstable stacking fault energy [Formula: see text]. This indicates that the presence of B will strengthen the TiAl/Ti3Al interface, but block its mobility. Further, the ratio of [Formula: see text]/[Formula: see text] of the B-doped system is 4.63%, 8.19% lower than that of the clean system. Based on the empirical criterions, B will have a negative effect on the ductility of the TiAl–Ti3Al alloy.

Rate Theory Modeling of Irradiation-induced Phosphorus Segregation in FCC nickel Using First Principles Calculations

2008 ◽  
Vol 1125 ◽  
Author(s):  
Ken-ichi Ebihara ◽  
Masatake Yamaguchi ◽  
Hideo Kaburaki ◽  
Yutaka Nishiyama
Keyword(s):  
First Principles ◽  
Interstitial Site ◽  
Theory Model ◽  
First Principles Calculation ◽  
Rate Theory ◽  
Vacancy Mechanism ◽  
First Principles Calculations ◽  
Phosphorus Segregation ◽  
Octahedral Interstitial Site ◽  
P Distribution

ABSTRACTWe have evaluated phosphorus (P) segregation in ion-irradiated nickel (Ni) by the rate theory model incorporating the results of first principles calculations. We find from our first principles calculation that the transport of P via the rotation mode of a mixed-dumbbell is unlikely to occur, and the transport coefficient of phosphorus by the vacancy mechanism is much larger than that reported previously. On the basis of our first principles results, we have also proposed to include the effect of free migration of P via the octahedral interstitial site of FCC Ni crystal in the rate theory model. With all these renewed parameters, we have successfully obtained the P distribution in irradiated Ni, which is very close to experiment, by adjusting the effect of P transport by the vacancy mechanism.

N--H Interaction in Nitrided Fe--Nb Alloys

2007 ◽  
Vol 539-543 ◽  
pp. 4987-4992
Author(s):  
Masatoshi Sakamoto
Keyword(s):  
Internal Friction ◽  
Room Temperature ◽  
Diffusion Rate ◽  
Interstitial Site ◽  
Torsion Pendulum ◽  
Nitriding Temperature ◽  
Octahedral Interstitial Site ◽  
Snoek Peak ◽  
Strong Affinity ◽  
Temperature Side

Internal friction of nitrogen in α iron has known as Snoek peak of N atom resolv ed in the octahedral interstitial site of bcc. When M atom ( Mn, Mo, Si, et.al) which has the affinity bigger than Fe were added ,another peaks due to the jump of N from Fe-Fe site to Fe-M site appear in the upper temperature side and complicate the Snoek peak curve of N. In this paper, the Snoek peak curve was studied in Fe-0.4wt%Nb-0.02wt%N alloys. This alloy showed no other peaks in the upper side to 373K and had only the single peak of N in Fe-Fe site. Internal friction measured by torsion pendulum method at about 1 Hz. After that this alloy was cooled from 373K to room temperature and reheated to 373K, but Snoek peak of N which showed on the first measurement just after nitriding disappeared completely and internal friction was only background. One of the reasons of it is the precipitation of Fe16N2 under heating and resolved N atoms disappeared. So these specimens were reheated to 873K and quenched, but Snoek peak of N was not measured. This shows the disappearance of N atom from Fe-Fe site. The mixture gas of a few % NH3 and H2 was used in this study. Therefore after nitriding much of H atoms were resolved in α iron alloys. Because the diffusion rate of H atom in α iron is bigger than N atom , it expected that H atoms can combine with Nb atoms before coming N atoms. And the appearance of Snoek peak of N in these alloys is considered. After that, in the heating to 373K H atom leave Nb and go away from the surface, and N atoms combine with Nb in place of H atoms. Nb has the very strong affinity with N, so these alloys have no peaks. When they reheated to the nitriding temperature N atoms can not diffuse from Fe-Nb site to Fe-Fe site. Then Snoek peak of N can not appears again in these alloys. Therefore, when Fe-Nb alloys were nitrided in NH3 and H2 mixture gas H atom plays very important part and it needs that the interaction of N-H atoms will be considered in these nitrided Fe-Nb alloys.

Effect of Additives on the Phase Equilibria Related to the E21-Fe3AlC Intermetalic Compound with Carbon Atom at the Interstitial Site

2002 ◽  
Vol 753 ◽  
Author(s):  
Hiroaki Ishii ◽  
Seiji Miura ◽  
Tetsuo Mohri
Keyword(s):  
Lattice Constant ◽  
Lattice Misfit ◽  
Interstitial Site ◽  
Lattice Parameter ◽  
The Body ◽  
Study Phase ◽  
Two Phase ◽  
Octahedral Interstitial Site ◽  
The Stability ◽  
Alloys And Compounds

ABSTRACTThe structure of E21 is a derivative of L12 structure with an interstitial carbon in the body center or the octahedral interstitial site. In the Fe-Al-C ternary system E21-Fe3AlC intermetallic is known to precipitate in γ-austenite alloys. For the high temperature application, the stability of microstructure is a key issue and the control of the lattice misfit is essential. By adding some elements to Fe-Al-C alloys, the lattice constant can be controlled, and enhancement of the stability of γ-austenite + E21-Fe3AlC two phase structure is expected. In this study, phase stability and lattice parameter of E21 phase in the (Fe-Mn)-(Al-M)-C system (M=Si, Ge) are investigated. In both systems, no significant changes in microstructures were observed within the composition range of concern. The lattice constant of E21-Fe3AlC phase, however, does not show decrease with the addition of Si or Ge. This result is different from what was expected. By WDS analysis, it was revealed that Si tends to distribute mainly in γ phase, and Ge concentrates in E21-Fe3AlC phase. It was found that the lattice constants of E21 phases are very close to those of L12 structure estimated from the atomic radii of constituent elements which are evaluated from those in binary alloys and compounds. The distribution behavior of Si and Ge can be related to tolerance factor which strongly affects the stability of phases.

SITE PREFERENCE AND ELASTIC PROPERTIES OF A2-Ti3Al WITH OXYGEN IMPURITY: A FIRST-PRINCIPLES STUDY

2010 ◽  
Vol 24 (15n16) ◽  
pp. 2749-2755 ◽  
Author(s):  
YE WEI ◽  
YING ZHANG ◽  
GUANG-HONG LU ◽  
HUIBIN XU
Keyword(s):  
Elastic Properties ◽  
First Principles ◽  
Density Functional ◽  
Interstitial Site ◽  
Site Preference ◽  
Oxygen Impurity ◽  
Functional Theory ◽  
Octahedral Interstitial Site ◽  
Tial Alloys ◽  
The Density Functional Theory

We employed a first-principles method based on the density functional theory to investigate the effect of impurity O on the site preference and elastic properties of α2- Ti 3 Al . We found that the O atom prefers to occupy the Ti -rich octahedral interstitial site in α2- Ti 3 Al . We calculated the elastic constants of α2- Ti 3 Al with single O atom, which demonstrate that the O presence has no large effect on α2- Ti 3 Al according to the empirical criterions. Other factors such as O cluster should be taken into account to understand the deleterious effect of O on α2- Ti 3 Al . Our results provide a useful reference to further study the mechanical properties of TiAl alloys.

Diffusion of Fission Gas in Uranium Dioxide: A First-Principles Study

2017 ◽  
Author(s):  
Qiang Zhao ◽  
Zheng Zhang ◽  
Yang Li ◽  
Xiaoping Ouyang
Keyword(s):  
Oxygen Vacancy ◽  
Uranium Dioxide ◽  
First Principles ◽  
Density Functional ◽  
Interstitial Site ◽  
First Principles Calculation ◽  
Spent Fuel ◽  
Octahedral Interstitial Site ◽  
Fission Gas ◽  
Vacancy Site

Uranium dioxide (UO2) is the typical fuel that is used in nuclear fission reactor, fission gas are produced during and after the reactor operation, and the fission gas have a significant impact on the performance of UO2 in reactor. In this paper, we investigated the effects of the fission gas on the performance of UO2 by using the first-principles calculation method based on the density functional theory. The results are that, the volume of UO2 increased when there is a fission gas atom enter in UO2 supercell; fission gas prefer to occupy the octahedral interstitial site over the uranium vacancy site and the oxygen vacancy site, and the oxygen vacancy site is the most difficult occupied site due to the formation of an oxygen vacancy is more difficult than that of the uranium vacancy; our results of the UO2 elastic constants are in good agreement with other simulation results and experimental data, and the fission gas atoms make the ductility of UO2 decreased. Our works may shed some light on the development of the UO2 fuel and the spent fuel reprocessing.

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