Trends in the structural stability of aluminum-rich transition-metal aluminides

1995 ◽  
Vol 51 (1) ◽  
pp. 169-172 ◽  
Author(s):  
J. Zou ◽  
C. L. Fu
Author(s):  
G.A. Botton ◽  
C.J. Humphreys

Transition metal aluminides are of great potential interest for high temperature structural applications. Although these materials exhibit good mechanical properties at high temperature, their use in industrial applications is often limited by their intrinsic room temperature brittleness. Whilst this particular yield behaviour is directly related to the defect structure, the properties of the defects (in particular the mobility of dislocations and the slip system on which these dislocations move) are ultimately determined by the electronic structure and bonding in these materials. The lack of ductility has been attributed, at least in part, to the mixed bonding character (metallic and covalent) as inferred from ab-initio calculations. In this work, we analyse energy loss spectra and discuss the features of the near edge structure in terms of the relevant electronic states in order to compare the predictions on bonding directly with spectroscopic experiments. In this process, we compare spectra of late transition metal (TM) to early TM aluminides (FeAl and TiAl) to assess whether differences in bonding can also be detected. This information is then discussed in terms of bonding changes at grain boundaries in NiAl.


2015 ◽  
Vol 33 (2) ◽  
pp. 251-258
Author(s):  
Bendouma Doumi ◽  
Allel Mokaddem ◽  
Mustapha Ishak-Boushaki ◽  
Miloud Boutaleb ◽  
Abdelkader Tadjer

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.


1995 ◽  
Vol 51 (13) ◽  
pp. 8102-8106 ◽  
Author(s):  
Mahalingam Balasubramanian ◽  
Douglas M. Pease ◽  
Joseph I. Budnick ◽  
Tariq Manzur ◽  
Dale L. Brewe

Author(s):  
Mohamed Helal ◽  
H. M. El-Sayed ◽  
Ahmed A Maarouf ◽  
Mohamed Fadlallah

Motivated by the successful preparation of two-dimensional transition metal dichalcogenides (2D- TMDs) nanomeshes in the last three years, we use density functional theory (DFT) to study the structural stability, mechanical,...


1991 ◽  
Vol 6 (6) ◽  
pp. 1188-1199 ◽  
Author(s):  
Jian-hua Xu ◽  
A.J. Freeman

The cohesive properties and electronic structures versus the structural stability of transition-metal trialuminides YAl3, ZrAl3, and NbAl3 in their cubic L12, tetragonal DO22, and naturally stable forms (i.e., the DO19 structure for YAl3 and the DO23 structure for ZrAl3) have been investigated using a total energy local-density approach. The variation of structural stability with transition-metal constituent can be simply understood in terms of the bandfilling of the bonding states in the rigid band sense, with the valence electrons gradually filling the bonding states on going from YAl3, ZrAl3 to NbAl3. This leads to a phase transition from the cubic L12 structure (for YAl3) to the tetragonal DO22 structure (for NbAl3). It is argued that this criterion may also apply to explain the variation of the structural stability of other transition-metal compounds (such as transition-metal carbides, nitrides, silicides, etc.) that are dominated by covalent interactions between the transition-metal d and the metalloid p states.


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