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.

Importance of Thermally Induced Magnetic Excitations in First-Principles Simulations of Elastic Properties of Transition Metal Alloys

2012 ◽  
Vol 190 ◽  
pp. 291-294
Author(s):  
Igor A. Abrikosov ◽  
Marcus Ekholm ◽  
Alena V. Ponomareva ◽  
Svetlana A. Barannikova
Keyword(s):  
Transition Metal ◽  
Elastic Properties ◽  
Ground State ◽  
First Principles ◽  
Magnetic Moments ◽  
Metal Alloys ◽  
Face Centered Cubic ◽  
Magnetic Ground State ◽  
Magnetic Excitations ◽  
Transition Metal Alloys

We demonstrate the importance of accounting for the complex magnetic ground state and finite temperature magnetic excitations in theoretical simulations of structural and elastic properties of transition metal alloys. Considering Fe72Cr16Ni12face centered cubic (fcc) alloy, we compare results of first-principles calculations carried out for ferromagnetic and non-magnetic states, as well as for the state with disordered local moments. We show that the latter gives much more accurate description of the elastic properties for paramagnetic alloys. We carry out a determination of the magnetic ground state for fcc Fe-Mn alloys, considering collinear, as well as non-collinear states, and show the sensitively of structural and elastic properties in this system to the detailed alignment between magnetic moments. We therefore conclude that it is essential to develop accurate models of the magnetic state for the predictive description of properties of transition metal alloys.

scholarly journals Study of Structural and Electronic Properties of Intercalated Transition Metal Dichalcogenides Compound MTiS2 (M = Cr, Mn, Fe) by Density Functional Theory

2021 ◽  
Keyword(s):  
Transition Metal ◽  
Band Structure ◽  
Electronic Properties ◽  
Density Of States ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Energy Band Structure ◽  
Functional Theory ◽  
Structural And Electronic Properties ◽  
Metal Dichalcogenides

In the present work, we have studied intercalated Transition Metal Dichalcogenides (TMDC) MTiS2 compounds (M = Cr, Mn, Fe) by Density Functional Theory (DFT) with Generalized Gradient Approximation (GGA). We have computed the structural and electronic properties by using first principle method in QUANTUM ESPRESSO computational code with an ultra-soft pseudopotential. A guest 3d transition metal M (viz; Cr, Mn, Fe) can be easily intercalated in pure transition metal dichalcogenides compound like TiS2. In the present work, the structural optimization, electronic properties like the energy band structure, density of states (DoS), partial or projected density of states (PDoS) and total density of states (TDoS) are reported. The energy band structure of MTiS2 compound has been found overlapping energy bands in the Fermi region. We conclude that the TiS2 intercalated compound has a small band gap while the doped compound with guest 3d-atom has metallic behavior as shown form its overlapped band structure.

scholarly journals Short-Range Structure of Ti0.63V0.27Fe0.10D1.73 from Neutron Total Scattering and Reverse Monte Carlo Modelling

Energies ◽  
2020 ◽  
Vol 13 (8) ◽  
pp. 1947
Author(s):  
Henrik Mauroy ◽  
Konstantin Klyukin ◽  
Marina G. Shelyapina ◽  
David A. Keen ◽  
Annett Thøgersen ◽  
...  
Keyword(s):  
Monte Carlo ◽  
Hydrogen Storage ◽  
Short Range ◽  
Density Functional ◽  
Metal Species ◽  
Face Centered Cubic ◽  
Reverse Monte Carlo ◽  
Hydrogen Atoms ◽  
Total Scattering ◽  
Neutron Total Scattering

Ti-V-based body-centered cubic (BCC) alloys have potential for large-scale hydrogen storage if expensive vanadium is substituted with much cheaper Fe-containing ferrovanadium. Use of ferrovanadium reduces the alloys’ hydrogen storage capacity. This is puzzling since the amount of Fe is low and hydrogen atoms are accommodated in interstitial sites which are partly coordinated by Fe in many intermetallic compounds. The present work is aimed at finding a structural explanation for Fe-induced capacity loss in Ti-V alloys. Since such alloys and their hydrides are highly disordered without long-range occupational order of the different metal species, it was necessary to employ a technique which is sensitive to local structure. Neutron total scattering coupled with reverse Monte Carlo modelling was thus employed to elucidate short-range atomic correlations in Ti0.63V0.27Fe0.10D1.73 from the pair distribution function. It was found that Fe atoms form clusters and that the majority of the vacant interstitial sites are within these clusters. These clusters take the same face-centered cubic structure as the Ti-V matrix in the deuteride and thus they are not simply unreacted Fe which has a BCC structure. The presence of Fe clusters is confirmed by transmission electron microscopy. Density functional theory calculations indicate that the clustering is driven by thermodynamics.

First-Principles Study on Mechanical Properties of IVB-Group Transition-Metal Nitrides TiN, ZrN, and HfN

2011 ◽  
Vol 415-417 ◽  
pp. 1451-1456
Author(s):  
Jin Wang ◽  
Zhi Qian Chen ◽  
Chun Mei Li ◽  
Fang Wang ◽  
Ying Zhong
Keyword(s):  
Mechanical Properties ◽  
Transition Metal ◽  
Elastic Properties ◽  
Density Of States ◽  
High Hardness ◽  
Metal Nitrides ◽  
Face Centered Cubic ◽  
Transition Metal Nitrides ◽  
Electronic Density ◽  
Good Thermal Stability

IVB-group transition-metal nitrides are hot research materials due to their high hardness, good thermal stability, and excellent mechanical properties. In this paper, we studied the lattice parameters, elastic properties, electronic structures, and hardness of the face centered cubic TiN, ZrN, and HfN. The research shows that all the three types have excellent elastic properties. According to the result, elastic properties of HfN are the best of the three, as its bulk modulus and shear modulus are 278GPa and 240GPa respectively. With the calculation of electronic density of states, we find that all the three types are metallic. The wide pseudogap in DOS and the large overlap population indicate the strong Ti-N, Zr-N, and Hf-N bonds. The lower value of the density of states on the Fermi level shows that crystal structure of HfN is more stable. That is why the elastic properties of HfN are better than the others, mainly. The calculated hardness of TiN is 23.6GPa, which is the highest.

Structural and Electronic Properties of Hydrogen-Passivated Silicon Quantum Dots: Density Functional Calculations

2015 ◽  
Vol 1107 ◽  
pp. 571-576 ◽  
Author(s):  
Muhammad Mus-'ab Anas ◽  
Ahmad Puaad Othman ◽  
Geri Gopir
Keyword(s):  
Quantum Dots ◽  
Density Functional ◽  
Energy Gap ◽  
Local Density ◽  
Basis Set ◽  
Face Centered Cubic ◽  
Hydrogen Atoms ◽  
Silicon Quantum Dots ◽  
Theoretical Approaches ◽  
Passivated Silicon

Density functional theory (DFT) by numerical basis-set calculations of silicon quantum dots (Si-QDs) passivated by hydrogen, ranging in size up to 1.9 nm are presented. These DFT computation results are used to examine and deduce the properties of 14 spherical Si-QDs including its density of state (DOS), and energy gap from the HOMO-LUMO results. The atomistic model of each silicon QDs was constructed by repeating crystal unit cell of face-centered cubic (FCC) structure, then the QDs surface was passivated by hydrogen atoms. The model was relaxed and optimized using Quasi-Newton method for each size of Si-QDs to get an ideal structure. Exchange-correlation potential (Vxc) of electrons were approximated in this system using the Local Density Approximation (LDA) functional and Perdew-Zunger (PZ) functional. Finally, all results were compared with previous experimental data and other similar theoretical approaches, and these results augured well

scholarly journals Tuning the Magnetic Moment of Small Late 3d-Transition-Metal Oxide Clusters by Selectively Mixing the Transition-Metal Constituents

Nanomaterials ◽  
2020 ◽  
Vol 10 (9) ◽  
pp. 1814
Author(s):  
Rodrigo H. Aguilera-del-Toro ◽  
María B. Torres ◽  
Faustino Aguilera-Granja ◽  
Andrés Vega
Keyword(s):  
Transition Metal ◽  
Metal Oxide ◽  
Magnetic Moment ◽  
Density Functional ◽  
Magnetic Moments ◽  
Metal Oxide Nanoparticles ◽  
Transition Metal Oxide ◽  
Blocking Temperature ◽  
Oxide Nanoparticles ◽  
Oxidation Rates

Transition-metal oxide nanoparticles are relevant for many applications in different areas where their superparamagnetic behavior and low blocking temperature are required. However, they have low magnetic moments, which does not favor their being turned into active actuators. Here, we report a systematical study, within the framework of the density functional theory, of the possibility of promoting a high-spin state in small late-transition-metal oxide nanoparticles through alloying. We investigated all possible nanoalloys An−xBxOm (A, B = Fe, Co, Ni; n = 2, 3, 4; 0≤x≤n) with different oxidation rates, m, up to saturation. We found that the higher the concentration of Fe, the higher the absolute stability of the oxidized nanoalloy, while the higher the Ni content, the less prone to oxidation. We demonstrate that combining the stronger tendency of Co and Ni toward parallel couplings with the larger spin polarization of Fe is particularly beneficial for certain nanoalloys in order to achieve a high total magnetic moment, and its robustness against oxidation. In particular, at high oxidation rates we found that certain FeCo oxidized nanoalloys outperform both their pure counterparts, and that alloying even promotes the reentrance of magnetism in certain cases at a critical oxygen rate, close to saturation, at which the pure oxidized counterparts exhibit quenched magnetic moments.

Structural, Electronic and Magnetic Properties of CaSe Doped with 3d (V, Cr and Mn)

SPIN ◽  
2021 ◽  
Author(s):  
Youcef Daoudi ◽  
Hadj Moulay Ahmed Mazouz ◽  
Brahim Lagoun ◽  
Ali Benghia
Keyword(s):  
Magnetic Properties ◽  
Transition Metal ◽  
Density Functional ◽  
Magnetic Moments ◽  
Plane Waves ◽  
Double Exchange ◽  
Spin Splitting ◽  
Full Potential ◽  
Generalized Gradient ◽  
Electronic And Magnetic Properties

We report first-principles investigation on structural, electronic and magnetic properties of 3d transition metal element-doped rock-salt calcium selenide Ca[Formula: see text]TMxSe (TM = V, Cr and Mn) at concentrations [Formula: see text] = 0.0625, 0.125 and 0.25. We performed the calculations in the framework of the density functional theory (DFT) using the full-potential linearized augmented plane waves plus local orbitals (FP-LAPW+lo) method within the Wu–Cohen generalized gradient approximation (WC-GGA) for the structural optimization and the Tran–Blaha modified Becke–Johnson (TBmBJ) potential for the electronic and the magnetic properties. The computed spin-polarized band structures and densities of states show that Ca[Formula: see text]CrxSe compounds at all studied concentrations are half-metallic ferromagnets with a complete spin polarization of 100% at Fermi-level while the Ca[Formula: see text]VxSe and Ca[Formula: see text]MnxSe are ferromagnetic semiconductors. The total magnetic moments for Ca[Formula: see text]VxSe, Ca[Formula: see text]CrxSe, and Ca[Formula: see text]MnxSe show the integer values of 3[Formula: see text][Formula: see text], 4[Formula: see text][Formula: see text], and 5[Formula: see text][Formula: see text], respectively, with a major contribution of transition metal elements (TM) in the total magnetization. Also, we reported the calculated exchange constants [Formula: see text] and [Formula: see text] and the band edge spin splitting of the valence ([Formula: see text]) and conduction ([Formula: see text]) bands. The ferromagnetism of these compounds is due to the super-exchange and the double-exchange mechanisms in addition to the strong p–d exchange interaction. Therefore, the predicted results indicate that the diluted Ca[Formula: see text]TMxSe (TM = V, Cr, Mn) compounds are suitable candidates for a possible application in the field of spintronic technology.

Electronic structure and magnetic properties of PbMO3 (M = Fe, Co, Ni) magnetic perovskites: An ab initio study

2014 ◽  
Vol 28 (29) ◽  
pp. 1450205 ◽  
Author(s):  
Aytaç Erkişi ◽  
Erdem Kamil Yıldırım ◽  
Gökhan Gökoğlu
Keyword(s):  
Transition Metal ◽  
Coulomb Interaction ◽  
Transition Metal Oxides ◽  
Density Functional ◽  
Magnetic Transition ◽  
Magnetic Moments ◽  
Local Spin Density Approximation ◽  
Electronic Band ◽  
Half Metallic ◽  
Hubbard U

We present the electronic, magnetic and structural properties of the magnetic transition metal oxides PbMO 3 (M = Fe , Co , Ni ) in cubic perovskite structure. The calculations are based on the density functional theory (DFT) within plane-wave pseudopotential method and local spin density approximation (LSDA) of the exchange-correlation functional. On-site Coulomb interaction is also included in calculations (LSDA+ U ). The systems are considered in ferromagnetic (FM) and G-type antiferromagnetic (G-AFM) order. FM structures are energetically more favored than G-AFM and than non-magnetic states for all the systems studied. The spin-polarized electronic band structures show that all the structures have metallic property in FM order without Hubbard-U interaction (U eff = 0). However, the inclusion of on-site Coulomb interaction (U eff = 7 eV ) opens a semiconducting gap for majority spin channel of PbFeO 3 and of PbNiO 3 resulting in a half-metallic character. PbCoO 3 system remains as metallic with LSDA+ U scheme. Bonding features of all structures are largely determined by the hybridizations between O–p and d-states of transition metal atoms. The partial magnetic moment of Fe atom in PbFeO 3 is enhanced by inclusion of Hubbard-U interaction (2.55 μB ⇒ 3.78 μB). Total magnetic moments of half-metallic PbFeO 3 and of PbNiO 3 compounds are very close to integer values.

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.

First-Principle Study on Half-Metallic Ferromagnetism and Structural Stability of C-Doped Alkaline-Earth Chalcogenides under Pressure

2014 ◽  
Vol 1052 ◽  
pp. 155-162
Author(s):  
Hui Zhao ◽  
Qian Han
Keyword(s):  
Density Of States ◽  
Density Functional ◽  
Magnetic Phase ◽  
Magnetic Moments ◽  
Second Order ◽  
Magnetic Phase Transitions ◽  
First Principle ◽  
Half Metallic ◽  
Lattice Constants ◽  
Cell Volumes

Three half-metallic ferromagnets with NaCl structure, X4CS3(X = Mg, Ca and Sr) are investigated by the first principle calculations based on the density functional theory in thegeneralized gradient approximation. Non-spin and spin polarized calculations are done to obtain the lattice constants, the equilibrium cell volumes, the stable energies and the magnetic moments of X4CS3, and band structure and density of states for X4CS3at high pressure are calculated. From the calculations it has been found that X4CS3is stable in the FM state. The corresponding lattice constants and the equilibrium cell volumes in FM are greater than that in NM. The magnetic moment of X4CS3decrease as pressure increases, and a second order magnetic phase transition of Sr4CS3from FM to NM state at pressure of 140GPa, but a second order magnetic phase transitions of Mg4CS3and Ca4CS3have not been found. According to the band and the density of states, as the pressure increases the half-metallic nature of X4CS3destroyed.

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