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.

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 Understanding Heteroatom-Mediated Metal–Support Interactions in Functionalized Carbons: A Perspective Review

2018 ◽  
Vol 8 (7) ◽  
pp. 1159 ◽  
Author(s):  
Sebastiano Campisi ◽  
Carine Chan-Thaw ◽  
Alberto Villa
Keyword(s):  
Liquid Phase ◽  
Metal Nanoparticles ◽  
Electronic Properties ◽  
Functional Groups ◽  
Theoretical Models ◽  
Alcohol Oxidation ◽  
Metal Interaction ◽  
Characterization Techniques ◽  
Metal Support ◽  
Metal Support Interactions

Carbon-based materials show unique chemicophysical properties, and they have been successfully used in many catalytic processes, including the production of chemicals and energy. The introduction of heteroatoms (N, B, P, S) alters the electronic properties, often increasing the reactivity of the surface of nanocarbons. The functional groups on the carbons have been reported to be effective for anchoring metal nanoparticles. Although the interaction between functional groups and metal has been studied by various characterization techniques, theoretical models, and catalytic results, the role and nature of heteroatoms is still an object of discussion. The aim of this review is to elucidate the metal–heteroatoms interaction, providing an overview of the main experimental and theoretical outcomes about heteroatom-mediated metal–support interactions. Selected studies showing the effect of heteroatom–metal interaction in the liquid-phase alcohol oxidation will be also presented.

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).

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.

Graphene-based gas sensor: metal decoration effect and application to a flexible device

2014 ◽  
Vol 2 (27) ◽  
pp. 5280-5285 ◽  
Author(s):  
Byungjin Cho ◽  
Jongwon Yoon ◽  
Myung Gwan Hahm ◽  
Dong-Ho Kim ◽  
Ah Ra Kim ◽  
...  
Keyword(s):  
Metal Nanoparticles ◽  
Electronic Properties ◽  
Gas Sensor ◽  
Gas Sensitivity ◽  
Flexible Device ◽  
Sensitivity And Selectivity ◽  
Metal Decoration ◽  
Synergistic Combination

Synergistic combination of metal nanoparticles and graphene modulates electronic properties of graphene, leading to enhancement in gas sensitivity and selectivity.

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.

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