scholarly journals Ab Initio Study of Martensitic Transformation in NiTiPt High Temperature Shape Memory Alloys

2021 ◽  
Vol 11 (15) ◽  
pp. 6878
Author(s):  
Xiaolan Yang ◽  
Jiaxiang Shang
Keyword(s):  
Phase Transition ◽  
Martensitic Transformation ◽  
Electronic Structures ◽  
Density Functional ◽  
Martensite Phase ◽  
Computational Results ◽  
Ab Initio Study ◽  
Functional Theory ◽  
Phase Transition Temperatures ◽  
Martensite Structure

The crystal structures and martensitic transformation of Ti50Ni50−xPtx alloys (x = 0, 6.25, 8.33, 10.42, 12.5, 18.75, 25) were studied by means of density functional theory (DFT). The computational results indicate that the lattice parameters of Ti-Ni-Pt alloys continuously increase with increasing the Pt content. It is found that at ≤ 12.5 at.% Pt, the martensite structure is monoclinic B19′ phase, and the energy differences between parent and martensite phases (ΔE) decrease slightly with a minimum observed at 6.25 at.% Pt. However, when the Pt content is increased to around 15 at.%, the most stable martensite phase is the orthorhombic B19 structure, and the ΔE increases sharply with Pt concentration. It was found that the phase transition temperatures are closely related to the energy differences ΔE between parent and martensite phases. The electronic structures of martensite B19 and B19′ phases are also discussed.

First-Principle Study on the Structural Phase Transition, and Electronic Structures of Cobalt under Pressure

2015 ◽  
Vol 729 ◽  
pp. 15-20
Author(s):  
Hong Bo Zhu ◽  
Dun Qiang Tan ◽  
Zhi Huang Xiong
Keyword(s):  
Phase Transition ◽  
Electronic Structures ◽  
Density Functional ◽  
Structural Parameters ◽  
Structural Phase ◽  
First Principles Calculation ◽  
Functional Theory ◽  
Calculated Equilibrium ◽  
Theoretical Results ◽  
Good Agreement

The structural phase transitions and electronic structures of Co are investigated by using the first-principles calculation based on density-functional theory (DFT). Our calculated equilibrium structural parameters of Co are in good agreement with the available experimental data and other theoretical results. The calculated phase transition hcp-Co → fcc-Co at ca. 125.25 GPa. The magnetic moment of hcp-Co and fcc-Co drops to zero at 155 GPa and 77 GPa, respectively.

Structural Phase Transition and Electronic Properties of MgCe under High Pressure from First-Principles Calculations

2014 ◽  
Vol 577 ◽  
pp. 102-107
Author(s):  
Qiu Xiang Liu ◽  
De Ping Lu ◽  
Rui Jun Zhang ◽  
Lei Lu ◽  
Shi Fang Xie
Keyword(s):  
Phase Transition ◽  
Ground State ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
High Pressures ◽  
Local Density ◽  
Structural Phase ◽  
First Principles Calculations ◽  
Functional Theory

The structural stability of MgCe under high pressures has been investigated by using the first-principles plane-wave pseudopotential density functional theory within the local density approximation (LDA). The obtained results predict that MgCe in the Ba structure is predicted to be the most stable structure corresponding to the ground state, because of lowest total energy. MgCe undergoes a pressure-induced phase transition from the Ba structure to B32 structure at 36 GPa. And no further transition is found up to 120 GPa. In addition, the electronic structures of four structures of MgCe are also calculated and discussed.

scholarly journals Comparative Study on Electronic Structure and Optical Properties of α-Fe2O3, Ag/α-Fe2O3 and S/α-Fe2O3

Metals ◽  
2021 ◽  
Vol 11 (3) ◽  
pp. 424
Author(s):  
Cuihua Zhao ◽  
Baishi Li ◽  
Xi Zhou ◽  
Jianhua Chen ◽  
Hongqun Tang
Keyword(s):  
Optical Properties ◽  
Optical Absorption ◽  
Electronic Structures ◽  
Density Functional ◽  
Peak Strength ◽  
Visible Range ◽  
High Symmetry ◽  
Functional Theory ◽  
Optical Absorption Peak ◽  
Calculation Results

The electronic structures and optical properties of pure, Ag-doped and S-doped α-Fe2O3 were studied using density functional theory (DFT). The calculation results show that the structure of α-Fe2O3 crystal changes after Ag and S doping, which leads to the different points of the high symmetry of Ag-doped and S-doped α-Fe2O3 with that of pure α-Fe2O3 in the energy band, as well as different Brillouin paths. In addition, the band gap of α-Fe2O3 becomes smaller after Ag and S doping, and the optical absorption peak shifts slightly toward the short wavelength, with the increased peak strength of S/α-Fe2O3 and the decreased peak strength of Ag/α-Fe2O3. However, the optical absorption in the visible range is enhanced after Ag and S doping compared with that of pure α-Fe2O3 when the wavelength is greater than 380 nm, and the optical absorption of S-doped α-Fe2O3 is stronger than that of Ag-doped α-Fe2O3.

scholarly journals Atoms in Highly Symmetric Environments: H in Rhodium and Cobalt Cages, H in an Octahedral Hole in MgO, and Metal Atoms Ca-Zn in C20 Fullerenes

Symmetry ◽  
2021 ◽  
Vol 13 (7) ◽  
pp. 1281
Author(s):  
Zikri Altun ◽  
Erdi Ata Bleda ◽  
Carl Trindle
Keyword(s):  
Density Functional Theory ◽  
Quantum Theory ◽  
Coordination Number ◽  
Electronic Structures ◽  
Density Functional ◽  
Functional Theory ◽  
Metal Atoms ◽  
Tetragonal Pyramidal ◽  
Non Covalent Interactions ◽  
Covalent Interactions

An atom trapped in a crystal vacancy, a metal cage, or a fullerene might have many immediate neighbors. Then, the familiar concept of valency or even coordination number seems inadequate to describe the environment of that atom. This difficulty in terminology is illustrated here by four systems: H atoms in tetragonal-pyramidal rhodium cages, H atom in an octahedral cobalt cage, H atom in a MgO octahedral hole, and metal atoms in C20 fullerenes. Density functional theory defines structure and energetics for the systems. Interactions of the atom with its container are characterized by the quantum theory of atoms in molecules (QTAIM) and the theory of non-covalent interactions (NCI). We establish that H atoms in H2Rh13(CO)243− trianion cannot be considered pentavalent, H atom in HCo6(CO)151− anion cannot be considered hexavalent, and H atom in MgO cannot be considered hexavalent. Instead, one should consider the H atom to be set in an environmental field defined by its 5, 6, and 6 neighbors; with interactions described by QTAIM. This point is further illustrated by the electronic structures and QTAIM parameters of M@C20, M=Ca to Zn. The analysis describes the systematic deformation and restoration of the symmetric fullerene in that series.

The Quantum Length Dependence of Conductance in Molecular Device: An Ab Initio Study

2010 ◽  
Vol 663-665 ◽  
pp. 519-522
Author(s):  
Cai Juan Xia ◽  
Han Chen Liu ◽  
Ying Tang Zhang
Keyword(s):  
Electronic Transport ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Molecular Device ◽  
Functional Theory ◽  
Length Dependence ◽  
Molecular Conductance ◽  
Homo Lumo ◽  
Molecular Compounds

By Applying Nonequilibrium Green’s Function Formalism Combined First-Principles Density Functional Theory, we Investigate the Electronic Transport Properties of Thiophene and Furan Molecules with Different Quantum Length. the Influence of HOMO-LUMO Gaps and the Spatial Distributions of Molecular Orbitals on the Electronic Transport through the Molecular Device Are Discussed in Detail. the Results Show that the Transport Behaviors Are Determined by the Distinct Electronic Structures of the Molecular Compounds. the Length Dependence of Molecular Conductance Exhibits its Diversity for Different Molecules.

Electronic structure of the thermoelectric materials PbTe and AgPb18SbTe20 from first-principles calculations

2010 ◽  
Vol 25 (6) ◽  
pp. 1030-1036 ◽  
Author(s):  
Pengxian Lu ◽  
Zigang Shen ◽  
Xing Hu
Keyword(s):  
Band Structure ◽  
Thermoelectric Properties ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Partial Density ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Scanning Transmission ◽  
Linearized Augmented Plane Wave

To investigate the effects of substituting Ag and Sb for Pb on the thermoelectric properties of PbTe, the electronic structures of PbTe and AgPb18SbTe20 were calculated by using the linearized augmented plane wave based on the density-functional theory of the first principles. By comparing the differences in the band structure, the partial density of states (PDOS), the scanning transmission microscope, and the electron density difference for PbTe and AgPb18SbTe20, we explained the reason from the aspect of electronic structures why the thermoelectric properties of AgPb18SbTe20 could be improved significantly. Our results suggest that the excellent thermoelectric properties of AgPb18SbTe20 should be attributed in part to the narrowing of its band gap, band structure anisotropy, the much extrema and large DOS near Fermi energy, as well as the large effective mass of electrons. Moreover, the complex bonding behaviors for which the strong bonds and the weak bonds are coexisted, and the electrovalence and covalence of Pb–Te bond are mixed should also play an important role in the enhancement of the thermoelectric properties of the AgPb18SbTe20.

scholarly journals Metal-Rich Metallaboranes: Synthesis, Structures and Bonding of Bi- and Trimetallic Open-Faced Cobaltaboranes

Inorganics ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 28
Author(s):  
Kriti Pathak ◽  
Chandan Nandi ◽  
Jean-François Halet ◽  
Sundargopal Ghosh
Keyword(s):  
Electronic Structures ◽  
Density Functional ◽  
Room Temperature ◽  
Electron Pair ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
X Ray ◽  
Cluster 2 ◽  
Cobalt Center

Synthesis, isolation, and structural characterization of unique metal rich diamagnetic cobaltaborane clusters are reported. They were obtained from reactions of monoborane as well as modified borohydride reagents with cobalt sources. For example, the reaction of [Cp*CoCl]2 with [LiBH4·THF] and subsequent photolysis with excess [BH3·THF] (THF = tetrahydrofuran) at room temperature afforded the 11-vertex tricobaltaborane nido-[(Cp*Co)3B8H10] (1, Cp* = η5-C5Me5). The reaction of Li[BH2S3] with the dicobaltaoctaborane(12) [(Cp*Co)2B6H10] yielded the 10-vertex nido-2,4-[(Cp*Co)2B8H12] cluster (2), extending the library of dicobaltadecaborane(14) analogues. Although cluster 1 adopts a classical 11-vertex-nido-geometry with one cobalt center and four boron atoms forming the open pentagonal face, it disobeys the Polyhedral Skeletal Electron Pair Theory (PSEPT). Compound 2 adopts a perfectly symmetrical 10-vertex-nido framework with a plane of symmetry bisecting the basal boron plane resulting in two {CoB3} units bridged at the base by two boron atoms and possesses the expected electron count. Both compounds were characterized in solution by multinuclear NMR and IR spectroscopies and by mass spectrometry. Single-crystal X-ray diffraction analyses confirmed the structures of the compounds. Additionally, density functional theory (DFT) calculations were performed in order to study and interpret the nature of bonding and electronic structures of these complexes.

Sign in / Sign up

Export Citation Format

Share Document