Electronic transport properties of the Al0.5TiZrPdCuNi alloy in the high-entropy alloy and metallic glass forms

Abstract

High-entropy alloys (HEAs) are characterized by a simultaneous presence of a crystal lattice and an amorphous-type chemical (substitutional) disorder. In order to unravel the effect of crystal-glass duality on the electronic transport properties of HEAs, we performed a comparative study of the electronic transport coefficients of a 6-component alloy Al0.5TiZrPdCuNi that can be prepared either as a HEA or as a metallic glass (MG) at the same chemical composition. The HEA and the MG states of the Al0.5TiZrPdCuNi alloy both show large, negative-temperature-coefficient resistivity, positive thermopower, positive Hall coefficient and small thermal conductivity. The transport coefficients were reproduced analytically by the spectral conductivity model, using the Kubo-Greenwood formalism. For both modifications of the material (HEA and MG), contribution of phonons to the transport coefficients was found small, so that their temperature dependence originates predominantly from the temperature dependence of the Fermi–Dirac function and the variation of the spectral conductivity and the related electronic density of states with energy within the Fermi-level region. The very similar electronic transport coefficients of the HEA and the MG states point towards essential role of the immense chemical disorder.

Evidence for isotropic s-wave superconductivity in high-entropy alloys

“… 13 . In contrast to other HEA types 24 , the zero or small binary mixing enthalpies of the constituent elements in TaNbZrHfTi HEAs favor the formation of a single phase structure, when depositing the HEA film on a substrate held at room temperature 13 . Consistent with our previous study of this compound 13 , the formation of a completely mixed single phase and the absence of other binary phases is confirmed by chemical mapping through energy-dispersive X-ray spectroscopy measurements with the scanning electron microscope.…”

A divide-and-conquer method to improve performance in quantum transport calculations: conductance in rotated graphene nanoribbons side-contact junctions

“…Now, to obtain an analytical estimation of the computational time required by this method, let us consider a square lattice of L × L sites. To determine the S-matrix of this system, first we have to calculate the S-matrices of four L 2 × L 2 subregions, and join them by applying equation ( 2) three times, where multiplications and inversions take a time that scales as O L 3 . Then, the time required to obtain the S-matrix of the L × L structure, time(L), satisfies the following recursive formula, where αL 3 encompasses the leading order terms of the three gluing steps and α depends only on the relative sizes of the gluing steps involved, which makes it a size-independent scalar.…”

“…Quantum transport is a wide field of study [1][2][3][4] for which there exist plenty of recursive methods to study it within the tight-binding approximation [5][6][7][8][9][10][11][12][13][14]. These methods are useful to calculate the Green's function, the transfer matrix, or the scattering matrix (S-matrix) of the system, which then can be used to obtain the transmission function T(E) at energy E [5,6].…”

“…However, for tight-binding structures, almost all elements of the Hamiltonian matrix are zero, therefore it is sparse. By using numerical methods suitable for sparse matrices, it has been reported [19] that for L ∼ 10 3 the computational times scales as O L 3 . But the performance in the memory usage is still better for recursive methods.…”

Al27 NMR local study of the Al0.5TiZrPdCuNi alloy in high-entropy alloy and metallic glass forms

“…Astonishingly, despite the vast literature on the formation, stability, structure, and physical-mechanical properties of HEAs [1][2][3][4][5], no * jani.dolinsek@ijs.si local spectroscopic study of HEAs with NMR [or other local technique like nuclear quadrupole resonance (NQR), electron paramagnetic resonance (EPR), Mössbauer spectroscopy, or perturbed γ -γ angular correlations] can be found in the literature at the time of writing. In this paper, we report a 27 Al NMR study of the lineshape and Knight shift of a six-component Al 0.5 TiZrPdCuNi metallic alloy that can be prepared either as a HEA or as a metallic glass (MG) at the same chemical composition [6][7][8]. For both structural modifications of the material (HEA and MG), we have determined the distribution of EFG tensors, which directly reflects the distribution of local chemical environments.…”