The Effect of Vacancy on the Phase Stability of TiNi Shape Memory Alloy from First-Principle Calculation

2011 ◽  
Vol 687 ◽  
pp. 528-532
Author(s):  
Bin Yue ◽  
Yan Li ◽  
Fei Zhang
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Phase Stability ◽  
Density Functional ◽  
Formation Enthalpy ◽  
Tini Alloy ◽  
First Principle ◽  
Generalized Gradient ◽  
First Principle Calculation ◽  
Formation Enthalpies

The effect of vacancy on the phase stability of TiNi shape memory alloy has been investigated by the first-principle method based on the density functional theory with generalized gradient approximation. The formation energy, formation heat, formation enthalpy per atom and density of states (DOS) of TiNi alloy with and without vacancy are calculated. The results indicate that the favorable point defect is Ni vacancy in both B2 and B19’ phases of TiNi alloy. The existence of vacancy increases the formation enthalpies per atom difference and thus decreases the phase stability. The DOS values at Fermi level of martensitic phases are lower than that of austenite phases in both perfect TiNi and TiNi with Ni vacancy, indicating the natural transformation from austenite to martensite upon cooling.

First Principle Calculation of Li2Fe0.5Cr0.5SiO4 for Li-Ion Battery Cathode

2015 ◽  
Vol 1112 ◽  
pp. 286-289
Author(s):  
Ganjar Kurniawan Sukandi ◽  
Triati Dewi Kencana Wungu ◽  
Ferry Iskandar
Keyword(s):  
Structural Change ◽  
Phase Stability ◽  
Density Functional ◽  
Positive Sign ◽  
Initial Structure ◽  
First Principle ◽  
Generalized Gradient ◽  
Principle Calculation ◽  
First Principle Calculation ◽  
Couple Reaction

First principle calculation based on Density Functional Theory and U correction (DFT+U) is used to investigate structural change while losing Li atom, average voltage for couple reaction, phase stability, and electronic structure of Li2Fe0.5Cr0.5SiO4. In this calculation, generalized gradient approach (GGA) of Perdew-Burke-Ernzerhof (PBE) is used for exchange-correlation functional. The initial structure of Li2Fe0.5Cr0.5SiO4 is obtained from the pmn21 structure of Li2FeSiO4 and then the Fe site is substituted by 50 % of Cr. The results of calculation show that the optimized Li2Fe0.5Cr0.5SiO4 has a monoclinic structure, which has little different with Li2FeSiO4 structure. Although the delithiated system (LiFe0.5Cr0.5SiO4) is taken into consideration, the structural geometry does not change significantly. It is indicated that the presence of Cr does not affect to the property of structural change. From the density of states (DOS) analysis, the presence of Cr causes the width of band gap become decrease. Therefore, the electronic properties change from insulator to semiconductor-like behavior. Average voltage for couple reaction M+2/ M+3 of Li2Fe0.5Cr0.5SiO4 is about 3.05 V which is lower than Li2FeSiO4. Furthermore, the formation energy for Li2Fe0.5Cr0.5SiO4 and all delithiation have a relatively positive sign compared with Li2FeSiO4 that mean that they have poor phase stability than Li2FeSiO4.

scholarly journals Electronic Structure of Vanadium-Doped TiO2 of Both Anatase and Rutile Based on Density Functional Theory (DFT) Approach

2018 ◽  
Vol 14 (1) ◽  
pp. 60
Author(s):  
Hari Sutrisno
Keyword(s):  
Density Functional Theory ◽  
Valence Band ◽  
Density Functional ◽  
Local Density ◽  
First Principle ◽  
High Concentration ◽  
Generalized Gradient ◽  
Functional Theory ◽  
First Principle Calculation ◽  
Intermediate Band

<p>Study of the theoretical  approah to calculate the band structure and density of states (DOS) of vanadium-doped TiO<sub>2</sub> of both anatase and rutile have been done. The first-principle calculations were done using supercell (2x1x1) method. The first-principle calculation of V-doped TiO<sub>2</sub> of both anatase and rutile were analyzed by density-functional theory (DFT) with generalized gradient approximation from Perdew-Burke-Ernzerhof (GGA+PBE), Perdew-Wang’s 1991 (GGA+PW91) and local density approximation (LDA) for exchange-correlation functionals. The calculation of electronic structures show that the V-doped TiO<sub>2</sub>-anatase with high concentration (7.93 %) in 24 atoms are direct- and indirect-gap semiconductor, whereas the V-doped TiO<sub>2</sub>-rutile with high concentration (15.79 %) in 12 atoms is direct-gap semiconductor. The V-doped TiO<sub>2</sub> of both anatase and rutile produce the intermediate bands in the upper states. Ihe V-doped anatase produces intermediate band, which is 2.05, 2.04, 2.06 eV above the valence band for GGA+PBE, GGA+PW91 and LDA, respectively. Meanwhile the V-doped rutile producesintermediate band, which is 1.76, 1.82, 1.74 eV above the valence band for GGA+PBE, GGA+PW91 and LDA, respectively.</p>

scholarly journals First-principle investigations of structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides

2015 ◽  
Vol 33 (2) ◽  
pp. 251-258
Author(s):  
Bendouma Doumi ◽  
Allel Mokaddem ◽  
Mustapha Ishak-Boushaki ◽  
Miloud Boutaleb ◽  
Abdelkader Tadjer
Keyword(s):  
Transition Metal ◽  
Electronic Properties ◽  
Density Functional ◽  
First Principle ◽  
Generalized Gradient ◽  
Metallic Behavior ◽  
Plane Wave Method ◽  
Structural And Electronic Properties ◽  
The Difference ◽  
Metal Aluminides

AbstractIn the present work, we have investigated the structural and electronic properties of TMAl (TM = Fe, Co, and Ni) transition metal aluminides in the B2 structure, using first-principle calculations of the density functional theory (DFT) based on the linearized augmented plane wave method (FP-LAPW) as implemented in the WIEN2k code, in which the energy of exchange and correlation are treated by the generalized gradient approximation (GGA), proposed in 1996 by Perdew, Burke and Ernzerhof (PBE). The ground state properties have been calculated and compared with other calculations, and the electronic structures of all FeAl, CoAl, and NiAl compounds exhibited a metallic behavior. It was depicted that the density of states is characterized by the large hybridization between the s-p (Al) and 3d (Fe, Co, and Ni) states, which creates the pseudogap in the region of anti-bonding states. Moreover, the band structures of FeAl, CoAl, and NiAl are similar to each other and the difference between them is in the energy level of each band relative to the Fermi level.

scholarly journals VIBRATIONAL MODES IN SMALL Agn, Aun CLUSTERS: A FIRST PRINCIPLE CALCULATION

2009 ◽  
Vol 23 (31) ◽  
pp. 5819-5834 ◽  
Author(s):  
OLCAY ÜZENGI AKTÜRK ◽  
OĞUZ GÜLSEREN ◽  
MEHMET TOMAK
Keyword(s):  
Normal Mode ◽  
Density Functional ◽  
Local Density ◽  
Scanning Tunneling ◽  
Generalized Gradient ◽  
Functional Formalism ◽  
First Principle Calculation ◽  
Pseudopotential Calculations ◽  
Normal Mode Calculations ◽  
Small Clusters

Although the stable structures and other physical properties of small Ag n and Au n, were investigated in the literature, phonon calculations are not done yet. In this work, we present plane-wave pseudopotential calculations based on density-functional formalism. The effect of using the generalized gradient approximation (GGA) and local density approximation (LDA) to determine the geometric and electronic structure and normal mode calculations of Ag n and Au n, is studied up to eight atoms. Pure Au n and Ag n clusters favor planar configurations. We calculated binding energy per atom. We have also calculated the normal mode calculations and also scanning tunneling microscope (STM) images for small clusters for the first time.

scholarly journals Tuning Electronic Structures of BN and C Double-Wall Hetero-Nanotubes

2015 ◽  
Vol 2015 ◽  
pp. 1-9 ◽  
Author(s):  
Xueran Liu ◽  
Meijun Han ◽  
Xinjiang Zhang ◽  
Haijun Hou ◽  
Shaoping Pang ◽  
...  
Keyword(s):  
Boron Nitride ◽  
Electric Field ◽  
Electronic Structures ◽  
Density Functional ◽  
Transverse Electric ◽  
First Principle ◽  
Generalized Gradient ◽  
Functional Theory ◽  
Generalized Gradient Approximation ◽  
Double Wall

First principle calculations based on density functional theory with the generalized gradient approximation were carried out to investigate the energetic and electronic properties of carbon and boron nitride double-wall hetero-nanotubes (C/BN-DWHNTs) with different chirality and size, including an armchair (n,n) carbon nanotube (CNT) enclosed in (m,m) boron nitride nanotube (BNNT) and a zigzag (n, 0) CNT enclosed in (m, 0) BNNT. The electronic structure of these DWHNTs under a transverse electric field was also investigated. The ability to tune the band gap with changing the intertube distance (di) and imposing an external electric field (F) of zigzag DWHNTs provides the possibility for future electronic and electrooptic nanodevice applications.

Current Density Contour Map of TiNi Shape Memory Alloy in Simulated Physiological Solutions

2007 ◽  
Vol 342-343 ◽  
pp. 573-576
Author(s):  
Woon Suk Hwang ◽  
Seung Chan Na ◽  
Jeong Ja Lee
Keyword(s):  
Sodium Chloride ◽  
Shape Memory Alloy ◽  
Shape Memory ◽  
Current Density ◽  
Localized Corrosion ◽  
Tini Alloy ◽  
Contour Map ◽  
Chloride Solutions ◽  
Sodium Chloride Solutions ◽  
Density Contour

In order to investigate the corrosion behavior of TiNi shape memory alloy, especially electrochemical behavior of pitting and crevice corrosion in a human body, current density contour(CDC) map of TiNi alloy was constructed by potentiodynamic polarization technique in simulated physiological sodium chloride solutions of pH ranging from 1 to 13 at 37oC. Morphology of pits and corrosion products in sodium chloride solutions of various pH were analyzed by SEM and EDX, and susceptibility and mechanism of localized corrosion were also discussed.

Structural, electronic and elastic properties of the shape memory alloy NbRu: First-principle investigations

2017 ◽  
Vol 695 ◽  
pp. 3024-3029 ◽  
Author(s):  
Peng Shao ◽  
Li-Ping Ding ◽  
Dao-Bin Luo ◽  
Jiang-Tao Cai ◽  
Cheng Lu ◽  
...  
Keyword(s):  
Shape Memory Alloy ◽  
Shape Memory ◽  
Elastic Properties ◽  
First Principle
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