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All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Simulated structure and thermodynamics of decagonal Al-Co-Cu quasicrystals

Atomic structures of Al-Co-Cu decagonal quasicrystals (dQCs) are investigated using empirical oscillating pair potentials (EOPP) in molecular dynamic (MD) simulations that we enhance by Monte Carlo (MC) swapping of chemical species and replica exchange. Predicted structures exhibit planar decagonal tiling patterns and are periodic along the perpendicular direction. We then recalculate the energies of promising structures using first-principles density functional theory (DFT), along with energies of competing phases. We find that our τ -inflated sequence of QC approximants (QCAs) are energetically unstable at low temperature by at least 3 meV/atom. Extending our study to finite temperatures by calculating harmonic vibrational entropy, as well as anharmonic contributions that include chemical species swaps and tile flips, our results suggest that the quasicrystal phase is entropically stabilized at temperatures in the range 600-800 K and above. It decomposes into ordinary (though complex) crystal phases at low temperatures, including a partially disordered B2-type phase. We discuss the influence of density and composition on QC phase stability; we compare the structural differences between Co-rich and Cu-rich quasicrystals; and we analyze the role of entropy in stabilizing the quasicrystal, concluding with a discussion of the possible existence of “high entropy” quasicrystals. Published by the American Physical Society 2024

Huang, Yang (ORCID:0009000045917347)↗
DOE OSTI2020

Materials Data on Al12Co4Cu by Materials Project

Co4CuAl12 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are ten inequivalent Co sites. In the first Co site, Co is bonded in a 9-coordinate geometry to one Cu and eight Al atoms. The Co–Cu bond length is 2.55 Å. There are a spread of Co–Al bond distances ranging from 2.27–2.60 Å. In the second Co site, Co is bonded in a 9-coordinate geometry to one Cu and eight Al atoms. The Co–Cu bond length is 2.55 Å. There are a spread of Co–Al bond distances ranging from 2.27–2.60 Å. In the third Co site, Co is bonded in a 10-coordinate geometry to eight Al atoms. There are a spread of Co–Al bond distances ranging from 2.40–2.57 Å. In the fourth Co site, Co is bonded in a 10-coordinate geometry to one Cu and nine Al atoms. The Co–Cu bond length is 2.57 Å. There are a spread of Co–Al bond distances ranging from 2.40–2.74 Å. In the fifth Co site, Co is bonded in a 10-coordinate geometry to ten Al atoms. There are a spread of Co–Al bond distances ranging from 2.38–2.72 Å. In the sixth Co site, Co is bonded in a 10-coordinate geometry to one Cu and nine Al atoms. The Co–Cu bond length is 2.59 Å. There are a spread of Co–Al bond distances ranging from 2.37–2.64 Å. In the seventh Co site, Co is bonded in a 10-coordinate geometry to eight Al atoms. There are a spread of Co–Al bond distances ranging from 2.40–2.57 Å. In the eighth Co site, Co is bonded in a 10-coordinate geometry to one Cu and nine Al atoms. The Co–Cu bond length is 2.57 Å. There are a spread of Co–Al bond distances ranging from 2.40–2.74 Å. In the ninth Co site, Co is bonded in a 10-coordinate geometry to ten Al atoms. There are a spread of Co–Al bond distances ranging from 2.38–2.72 Å. In the tenth Co site, Co is bonded in a 10-coordinate geometry to one Cu and nine Al atoms. The Co–Cu bond length is 2.59 Å. There are a spread of Co–Al bond distances ranging from 2.37–2.64 Å. There are three inequivalent Cu sites. In the first Cu site, Cu is bonded in a 10-coordinate geometry to three Co and seven Al atoms. There are a spread of Cu–Al bond distances ranging from 2.41–2.65 Å. In the second Cu site, Cu is bonded in a 10-coordinate geometry to three Co and seven Al atoms. There are a spread of Cu–Al bond distances ranging from 2.41–2.65 Å. In the third Cu site, Cu is bonded in a distorted cuboctahedral geometry to two Co and ten Al atoms. There are a spread of Cu–Al bond distances ranging from 2.55–3.11 Å. There are twenty-four inequivalent Al sites. In the first Al site, Al is bonded in a 3-coordinate geometry to three Co atoms. In the second Al site, Al is bonded in a 2-coordinate geometry to three Co and two Al atoms. There are one shorter (2.70 Å) and one longer (2.84 Å) Al–Al bond lengths. In the third Al site, Al is bonded in a 12-coordinate geometry to three Co, one Cu, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.70–2.95 Å. In the fourth Al site, Al is bonded in a 5-coordinate geometry to three Co, two Cu, and two Al atoms. The Al–Al bond length is 2.73 Å. In the fifth Al site, Al is bonded in a 3-coordinate geometry to two Co, one Cu, and one Al atom. The Al–Al bond length is 2.70 Å. In the sixth Al site, Al is bonded in a 4-coordinate geometry to four Co and two Al atoms. The Al–Al bond length is 2.73 Å. In the seventh Al site, Al is bonded in a 3-coordinate geometry to three Co atoms. In the eighth Al site, Al is bonded in a 2-coordinate geometry to three Co and two Al atoms. The Al–Al bond length is 2.84 Å. In the ninth Al site, Al is bonded in a 3-coordinate geometry to three Co and two equivalent Al atoms. In the tenth Al site, Al is bonded in a 12-coordinate geometry to two Co, one Cu, and four Al atoms. Both Al–Al bond lengths are 2.76 Å. In the eleventh Al site, Al is bonded in a 4-coordinate geometry to three Co and one Cu atom. In the twelfth Al site, Al is bonded in a distorted linear geometry to two Co and one Al atom. The Al–Al bond length is 2.73 Å. In the thirteenth Al site, Al is bonded in a 3-coordinate geometry to three Co and two equivalent Al atoms. Both Al–Al bond lengths are 2.81 Å. In the fourteenth Al site, Al is bonded in a 12-coordinate geometry to two Co, one Cu, and four Al atoms. Both Al–Al bond lengths are 2.89 Å. In the fifteenth Al site, Al is bonded in a distorted linear geometry to two Co and one Al atom. The Al–Al bond length is 2.73 Å. In the sixteenth Al site, Al is bonded in a 11-coordinate geometry to four Co, one Cu, and six Al atoms. There are a spread of Al–Al bond distances ranging from 2.62–2.73 Å. In the seventeenth Al site, Al is bonded in a 4-coordinate geometry to four Co atoms. In the eighteenth Al site, Al is bonded in a 11-coordinate geometry to four Co, one Cu, and six Al atoms. In the nineteenth Al site, Al is bonded in a 4-coordinate geometry to four Co atoms. In the twentieth Al site, Al is bonded in a distorted linear geometry to two equivalent Co, one Cu, and two equivalent Al atoms. Both Al–Al bond lengths are 2.95 Å. In the twenty-first Al site, Al is bonded in a linear geometry to two equivalent Co, one Cu, and two equivalent Al atoms. In the twenty-second Al site, Al is bonded in a 3-coordinate geometry to two Co, one Cu, and one Al atom. In the twenty-third Al site, Al is bonded in a 5-coordinate geometry to three Co, two Cu, and two Al atoms. The Al–Al bond length is 2.73 Å. In the twenty-fourth Al site, Al is bonded in a 12-coordinate geometry to three Co, one Cu, and eight Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al7CoCu2 by Materials Project

Al7CoCu2 crystallizes in the tetragonal P4/mnc space group. The structure is three-dimensional. Co is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Co–Al bond distances ranging from 2.44–2.49 Å. Cu is bonded in a 10-coordinate geometry to two equivalent Cu and eight Al atoms. Both Cu–Cu bond lengths are 2.55 Å. There are a spread of Cu–Al bond distances ranging from 2.54–2.66 Å. There are three inequivalent Al sites. In the first Al site, Al is bonded in a 1-coordinate geometry to one Co and four equivalent Cu atoms. In the second Al site, Al is bonded in a 2-coordinate geometry to two equivalent Co atoms. In the third Al site, Al is bonded in a 4-coordinate geometry to one Co and three equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Al6CoCu3 by Materials Project

CoCu3Al6 crystallizes in the trigonal P3m1 space group. The structure is three-dimensional. Co is bonded in a 8-coordinate geometry to eight Al atoms. There are a spread of Co–Al bond distances ranging from 2.40–2.57 Å. There are three inequivalent Cu sites. In the first Cu site, Cu is bonded in a distorted body-centered cubic geometry to eight Al atoms. There are a spread of Cu–Al bond distances ranging from 2.49–2.61 Å. In the second Cu site, Cu is bonded in a distorted body-centered cubic geometry to eight Al atoms. There are a spread of Cu–Al bond distances ranging from 2.48–2.61 Å. In the third Cu site, Cu is bonded in a distorted body-centered cubic geometry to eight Al atoms. There are a spread of Cu–Al bond distances ranging from 2.45–2.58 Å. There are six inequivalent Al sites. In the first Al site, Al is bonded in a 5-coordinate geometry to one Co and four Cu atoms. In the second Al site, Al is bonded in a 5-coordinate geometry to one Co and four Cu atoms. In the third Al site, Al is bonded in a 5-coordinate geometry to three equivalent Co and two Cu atoms. In the fourth Al site, Al is bonded in a 5-coordinate geometry to five Cu atoms. In the fifth Al site, Al is bonded in a 6-coordinate geometry to six Cu atoms. In the sixth Al site, Al is bonded in a 6-coordinate geometry to three equivalent Co and three equivalent Cu atoms.

36 MATERIALS SCIENCE↗