scholarly journals Site Occupancies in Ternary C15 Ordered Laves Phases

1996 ◽  
Vol 460 ◽  
Author(s):  
P. G. Kotula ◽  
I. M. Anderson ◽  
F. Chu ◽  
D. J. Thoma ◽  
J. Bentley ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Total Energy ◽  
Phase Diagrams ◽  
First Principles ◽  
Site Occupancy ◽  
Electronic Structure Calculations ◽  
Laves Phase ◽  
Laves Phases ◽  
Structure Calculations

ABSTRACTSite occupancies in three C15-structured AB2(X) Laves phases have been determined with Atom Location by CHanneling Enhanced MIcroanalysis (ALCHEMI). In NbCr2(V), the results are consistent with exclusive site occupancies of Nb for the A sublattice and Cr and V for the A sublattice. The B-site occupancy of V can be interpreted in terms of electronic structure. In NbCr2(Ti), the results are consistent with Ti partitioning mostly to the A sites with some anti-site defects likely. In HfV2(Nb), the results are consistent with Nb partitioning between the A and A sites. The results of the ALCHEMI analyses of these ternary C15 Laves phase materials are discussed with respect to previously determined phase diagrams and first-principles total energy and electronic structure calculations.

Effect of Boron and Hydrogen on the Electronic Structure of Ni3Al

1993 ◽  
Vol 319 ◽  
Author(s):  
N. Kioussis ◽  
H. Watanabe ◽  
R.G. Hemker ◽  
W. Gourdin ◽  
A. Gonis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Charge Density ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Interstitial Site ◽  
Octahedral Interstitial Site ◽  
Interstitial Region ◽  
Ordered Intermetallic ◽  
Lmto Method ◽  
Structure Calculations

AbstractUsing first-principles electronic structure calculations based on the Linear-Muffin-Tin Orbital (LMTO) method, we have investigated the effects of interstitial boron and hydrogen on the electronic structure of the L12 ordered intermetallic Ni3A1. When it occupies an octahedral interstitial site entirely coordinated by six Ni atoms, we find that boron enhances the charge distribution found in the strongly-bound “pure” Ni3AI crystal: Charge is depleted at Ni and Al sites and enhanced in interstitial region. Substitution of Al atoms for two of the Ni atoms coordinating the boron, however, reduces the interstitial charge density between certain atomic planes. In contrast to boron, hydrogen appears to deplete the interstitial charge, even when fully coordinated by Ni atoms. We suggest that these results are broadly consistent with the notion of boron as a cohesion enhancer and hydrogen as an embrittler.

scholarly journals First principles methods using CASTEP

2005 ◽  
Vol 220 (5/6) ◽  
Author(s):  
Stewart J. Clark ◽  
Matthew D. Segall ◽  
Chris J. Pickard ◽  
Phil J. Hasnip ◽  
Matt I. J. Probert ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Future Development ◽  
First Principles ◽  
Electronic Structure Calculations ◽  
Development Plans ◽  
Near Future ◽  
Structure Calculations

AbstractThe CASTEP code for first principles electronic structure calculations will be described. A brief, non-technical overview will be given and some of the features and capabilities highlighted. Some features which are unique to CASTEP will be described and near-future development plans outlined.

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