AB-Initio Based Calculations of Vacancy Formation and Clustering Energies Including Lattice Relaxation in Fe3Al

1998 ◽  
Vol 538 ◽  
Author(s):  
Leonid S. Muratov ◽  
Bernard R. Cooper

AbstractVacancy formation and clustering significantly affect structural properties of transition-metal aluminides. Ab-initio quantum mechanical total-energy calculations using a full-potential linear combination of muffin-tin orbitals (LMTO) technique provide a convenient method of studying relevant characteristics such as changes in density of states, and charge redistribution around defects. Augmented with Hellmann-Feymann forces, LMTO allows calculations of relaxation geometries and relaxation energies. We have performed such calculations for vacancies and antisite substitutional point defects in Fe3Al with DO3 crystallographic structure. There are two limiting factors complicating calculations of defect formation energies directly from ab-inito calculations. The first is that a single defect, due to the lattice periodicity necessitated by the use of ab-inito total energy techniques, cannot be considered as an isolated defect, even in the maximum computable simulation cell. Unlike previous calculations [ I ], which did not find a dependency on the size of the simulation cell, our calculations have shown a significant difference in results for 32- and 16- atom cells. This difference provides information about vacancy clustering since it can be explained by a relatively small attractive interaction energy ~0.2 eV between two vacancies located in adjacent simulation cells and separated by the lattice constant distance (5.52Å) [2]. By comparing the internal energies for two configurations of 30 atom cells (32 atom - 2 vacancies) we were able to estimate that the attractive interaction between two vacancies could reach 1.2 eV. The second complication is the fact that chemical potentials of elements cannot be directly extracted from the total energy calculations for the compound. To deal with this problem, we considered two possible approximations and compared results, which were found to be quite similar for iron vacancies.

1988 ◽  
Vol 141 ◽  
Author(s):  
David L. Price ◽  
Bernard R. Cooper

AbstractWe discuss calculations of the electronic and crystallographic structure at the interfaces of titanium-carbon and tungsten-carbon superlattices. Specifically, we present total energy calculations for an arrangement of atoms designed to allow direct investigation of the competition between the formation of M-C bonds and C-C bonds. We conclude that the equilibrium structure is dominated by C-C bonding and so find that the interface has a graphite-like atomic arrangement rather than a carbide-like arrangement. These total energy calculations have been performed using a recently developed self-consistent linear combination of muffin-tin orbitals electronic structure method. This is a full-potential, all-electron, variation on standard LMTO electronic structure methods and, along with careful self-consistent determination of the parameters involved, allows accurate total energy calculations of the type of low symmetry systems involved in this study.


2006 ◽  
Vol 89 (7) ◽  
pp. 071913 ◽  
Author(s):  
Chang-Zeng Fan ◽  
Song-Yan Zeng ◽  
Zai-Ji Zhan ◽  
Ri-Ping Liu ◽  
Wen-Kui Wang ◽  
...  

1998 ◽  
Vol 78 (5-6) ◽  
pp. 417-422 ◽  
Author(s):  
R. Zeller ◽  
M. Asato ◽  
T. Hoshino ◽  
J. Zabloudil ◽  
P. Weinberger ◽  
...  

2008 ◽  
Vol 129 (23) ◽  
pp. 234105 ◽  
Author(s):  
Chao-Hao Hu ◽  
A. R. Oganov ◽  
Y. M. Wang ◽  
H. Y. Zhou ◽  
A. Lyakhov ◽  
...  

2004 ◽  
Vol 298 (1-3) ◽  
pp. 135-140 ◽  
Author(s):  
F. Chiker ◽  
B. Abbar ◽  
H. Aourag ◽  
A. Tadjer ◽  
S. Bresson ◽  
...  

1991 ◽  
Vol 02 (01) ◽  
pp. 288-291
Author(s):  
G. BROCKS ◽  
P.J. KELLY ◽  
R. CAR

The binding sites for adsorption of a single Si atom on the reconstructed Si (100) surface are identified using first-principles total energy calculations. By mapping out the total energy as a function of the position of the adatom on the surface, we establish several saddle points for migration over the surface. Similar calculations for P and Al adatoms establish the most important chemical trend.


2013 ◽  
Vol 114 (17) ◽  
pp. 174108 ◽  
Author(s):  
J. M. Vielma ◽  
G. Schneider

Sign in / Sign up

Export Citation Format

Share Document