Predicting metastable phase boundaries in Al–Cu alloys from first-principles calculations of free energies: The role of atomic vibrations

2006 ◽  
Vol 73 (5) ◽  
pp. 719-725 ◽  
Author(s):  
C Ravi ◽  
C Wolverton ◽  
V Ozoliņš
Keyword(s):  
First Principles ◽  
Metastable Phase ◽  
First Principles Calculations ◽  
Free Energies ◽  
Phase Boundaries ◽  
Cu Alloys ◽  
Atomic Vibrations

Benchmark First-Principles Calculations of Adsorbate Free Energies

ACS Catalysis ◽  
2018 ◽  
Vol 8 (3) ◽  
pp. 1945-1954 ◽  
Author(s):  
Anshumaan Bajpai ◽  
Prateek Mehta ◽  
Kurt Frey ◽  
Andrew M. Lehmer ◽  
William F. Schneider
Keyword(s):  
First Principles ◽  
First Principles Calculations ◽  
Free Energies

An effective and efficient approach to p-type AlN by Be2:O codoping from first-principles calculations

2016 ◽  
Vol 30 (20) ◽  
pp. 1650257
Author(s):  
Meng Zhao ◽  
Wenjun Wang ◽  
Jun Wang ◽  
Junwei Yang ◽  
Weijie Hu ◽  
...  
Keyword(s):  
First Principles ◽  
Ionization Energy ◽  
Hole Concentration ◽  
Valence Band Maximum ◽  
First Principles Calculations ◽  
Mutual Compensation ◽  
Efficient Approach ◽  
P Type ◽  
Codoping Method

Various Be:O-codoped AlN crystals have been investigated via first-principles calculations to evaluate the role of the different combinations in effectively and efficiently inducing p-type carriers. It is found that the O atom is favored to bond with two Be atoms. The formed Be2:O complexes decrease the acceptor ionization energy to 0.11 eV, which is 0.16 eV lower than that of an isolated Be in AlN, implying that the hole concentration could probably be increased by 2–3 orders of magnitude. The electronic structure of Be2:O-codoped AlN shows that the lower ionization energy can be attributed to the interaction between Be and O. The Be–O complexes, despite failing to induce p-type carriers for the mutual compensation of Be and O, introduce new occupied states on the valence-band maximum (VBM) and hence the energy needed for the transition of electrons to the acceptor level is reduced. Thus, the Be2:O codoping method is expected to be an effective and efficient approach to realizing p-type AlN.

Computational and Experimental Insights into the Role of Acidic Molecules on the Corrosion Behavior on 7A46 Aluminum Alloy

2021 ◽  
Vol 21 (4) ◽  
pp. 2221-2233
Author(s):  
Yaru Liu ◽  
Qinglin Pan ◽  
Xiangdong Wang ◽  
Ye Ji ◽  
Qicheng Liu ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Aluminum Alloy ◽  
Corrosion Behavior ◽  
First Principles ◽  
First Principles Calculations ◽  
Corrosive Media ◽  
Corrosion Depth ◽  
Corrosion Mechanisms ◽  
Nanoscale Level

The corrosion mechanisms for different corrosive media on the aged 7A46 aluminum alloy were systematically investigated at nanoscale level. The combination of empirical intergranular and exfoliation corrosion behavior was employed, and coupled with first-principles calculations. Results revealed that the dispersed distribution of matrix precipitates (MPs) leads to the enhancement of the corrosion resistance pre-ageing (PA) followed by double-ageing (PA-DA) alloy. The deepest corrosion depth of PA-DA alloy was in hydrochloric acid, and the calculation result demonstrates that the passivation effect in combination with the accumulation of corrosion products in nitric acid protect the PA-DA alloy from further corrosion.

Phase Stability and Role of Ternary Additions on Electronic and Mechanical Properties of Aluminum Intermetallics

1990 ◽  
Vol 213 ◽  
Author(s):  
A.J. Freeman ◽  
T. Hong ◽  
W. Lin ◽  
Jian-Hua Xu
Keyword(s):  
Mechanical Properties ◽  
Phase Stability ◽  
First Principles ◽  
Local Density ◽  
Electronic Charge ◽  
Intermetallic Alloys ◽  
Phase Boundaries ◽  
Bonding Properties ◽  
Ternary Additions

ABSTRACTFirst principles total energy local density method have addressed the problems of (i) bonding, cohesion and phase stability and (ii) the role of ternary additions, anti-phase boundaries (APB's) and other faults in determining the structural, electronic and mechanical properties of aluminum intermetallic alloys. A key goal has been to attempt to understand, at the electronic level, fundamental quantities that may be related to the crucial brittleness vs. ductility issue in high temperature Ni and Ti and other aluminides. Other contrasts between observed ductility properties of related systems (e.g., NiAl and RuAl) are related to their differing electronic and bonding properties, particularly the nature of p-d hybridization and the directional properties of their electronic charge distrubutions - especially for states near the Fermi energy.

The Role of Phase Stability in Ductile, Ordered B2 Intermetallics

2006 ◽  
Vol 980 ◽  
Author(s):  
James R. Morris ◽  
Yiying Ye ◽  
Maja Krcmar ◽  
Chong Long Fu
Keyword(s):  
Phase Stability ◽  
First Principles ◽  
Tensile Ductility ◽  
Stacking Faults ◽  
Low Energy ◽  
First Principles Calculations ◽  
Phase Competition ◽  
Transformation Pathway ◽  
Shape Memory Materials

AbstractWe discuss the underlying atomistic mechanism for experimentally observed large tensile ductility in various strongly ordered B2 intermetallic compounds. First-principles calculations demonstrate that all of the compounds exhibit little energy differences between the B2, B27 and B33 phases. These calculations relate observations of ductility in YAg, YCu and ZrCo to shape-memory materials including NiTi. One transformation pathway between the B2 and B33 phases establishes a connection between this phase competition, and stacking faults on the {011}B2 plane. The low energy of such a stacking fault will lead to splitting of the b=<100> dislocations into b/2 partials, observed in ZrCo, TiCo, and in the B19' phase of NiTi. Calculations demonstrate that this pathway is competitive with the traditional pathway for NiTi.

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