First-principles calculations for vacancy formation energies in Cu-based alloys

Geometric and electronic properties and vacancy formation energies for two kinds of oxygen-vacancy Cu 2 O (111) surfaces have been investigated by first-principles calculations. Results show that the relaxation happens mainly on the top three trilayers of surfaces. Two vacancies trap electrons of -0.11e and -0.27e, respectively. The effects of oxygen vacancies on the electronic structures are found rather localized. The electronic structures suggest that the oxygen vacancies enhance the electron donating ability of the surfaces to some extent. The energies of 1.75 and 1.43 eV for the formation of oxygen vacancies are rather low, which indicates the partially reduced surfaces are stable and easy to produce.

Download Full-text

Stability and Structures of Constitutional Defects in Nonstoichiometric Intermetallic Compounds by First-Principles Calculations

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3111 ◽

2005 ◽

Vol 475-479 ◽

pp. 3111-3114

Author(s):

Masataka Mizuno ◽

Hideki Araki ◽

Yasuharu Shirai

Keyword(s):

Intermetallic Compounds ◽

First Principles ◽

Electronic Structures ◽

Stoichiometric Composition ◽

Electronic Structure Calculations ◽

First Principles Calculations ◽

Compositional Dependence ◽

Wide Range ◽

Formation Energies ◽

Structure Calculations

Some of intermetallic compounds exist in a wide range of concentration around the stoichiometric composition. First-principles electronic structure calculations have been performed for constitutional defects in non-stoichiometric CoAl and CoTi in order to investigate their stabilities and structural relaxations induced by constitutional defects. For the evaluation of stabilities of constitutional defects, the compositional dependence curves both of formation energies and of lattice parameters are obtained by the calculations employing supercells in various sizes. The lattice relaxations around constitutional defects are discussed by analyzing the change in electronic structures induced by constitutional defects.

Download Full-text

First-Principles Calculations of Titanium Dopants in Alumina

Materials Science Forum ◽

10.4028/www.scientific.net/msf.475-479.3095 ◽

2005 ◽

Vol 475-479 ◽

pp. 3095-3098

Author(s):

Katsuyuki Matsunaga ◽

Teruyasu Mizoguchi ◽

Atsutomo Nakamura ◽

Takahisa Yamamoto ◽

Yuichi Ikuhara

Keyword(s):

Band Gap ◽

First Principles ◽

Electronic Structures ◽

First Principles Calculations ◽

Pseudopotential Calculations ◽

Formation Energies

First-principles pseudopotential calculations were performed to investigate atomic and electronic structures of titanium (Ti) dopants in alumina (Al2O3). It was found that a substitutional Ti3+ defect induced an extra level occupied by one electron within the band gap of Al2O3. When two or more substitutional Ti3+ defects were located closely to each other, the defect-induced levels exhibited strong bonding interactions, and their formation energies decreased with increasing numbers of Ti3+ defects. This indicates that association and clustering of substitutional Ti3+ defects in Al2O3 can take place due to the interaction of the defect-induced levels.

Download Full-text

New Pt-based Superalloy System Designed from First Principles

MRS Proceedings ◽

10.1557/proc-1128-u05-28 ◽

2008 ◽

Vol 1128 ◽

Author(s):

Vsevolod I. Razumovskiy ◽

Eyvaz I. Isaev ◽

Andrei V. Ruban ◽

Pavel A. Korzhavyi

Keyword(s):

Elastic Properties ◽

First Principles ◽

Defect Formation ◽

Alloy System ◽

First Principles Calculations ◽

Phonon Spectra ◽

Ultrahigh Temperature ◽

New Generation ◽

Formation Energies ◽

Temperature Applications

AbstractPt-Sc alloys with the γ-γ′ microstructure are proposed as a basis for a new generation of Pt-based superalloys for ultrahigh-temperature applications. This alloy system was identified on the basis of first-principles calculations. Here we discuss the prospects of the Pt-Sc alloy system on the basis of calculated elastic properties, phonon spectra, and defect formation energies.

Download Full-text

First-principles calculational methods for surface-vacancy formation energies, heats of segregation, and surface core-level shifts

Physical Review B ◽

10.1103/physrevb.39.4866 ◽

1989 ◽

Vol 39 (8) ◽

pp. 4866-4872 ◽

Cited By ~ 49

Author(s):

Peter J. Feibelman

Keyword(s):

First Principles ◽

Core Level ◽

Vacancy Formation ◽

Level Shifts ◽

Surface Vacancy ◽

Formation Energies

Download Full-text