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11 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

First principles prediction of the Al-Li phase diagram including configurational and vibrational entropic contributions

The whole Al-Li phase diagram is predicted from first principles calculations and statistical mechanics including the effect of configurational and vibrational entropy. The formation enthalpy of different configurations at different temperatures was accurately predicted by means of cluster expansions that were fitted from first principles calculations. The vibrational entropic contribution of each configuration was determined from the bond length vs. bond stiffness relationships for each type of bond and the Gibbs free energy of the different phases was obtained as a function of temperature from Monte Carlo simulations. The predicted phase diagram was in excellent agreement with the currently accepted experimental one in terms of the stable (AlLi, Al 2 Li 3 , AlLi 2 , Al 4 Li 9 ) and metastable (Al 3 Li) phases, of the phase boundaries between them and of the maximum stability temperature of line compounds. In addition, it provided accurate information about the gap between Al 3 Li and AlLi solvus lines. Finally, the influence of the vibrational entropy on the correct prediction of the phase diagram is discussed. Overall, the methodology shows that accurate phase diagrams of alloys of technological interest can be predicted from first principles calculations.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Origin of strain softening in a nanograined Al alloy

Here, one-step and multi-step nanoindentation experiments were conducted to investigate the mechanical response of an Al-Mg-Li alloy. Opposite to the strain hardening effect observed in the coarse-grained (CG) alloy, the nanograined (NG) alloy exhibits strain softening. Compared with multi-step nanoindentation experiments, the ultralow dislocation density and the grain boundary (GB) segregation promote a higher stress level during one-step nanoindentation experiments. Residual perfect dislocations induced by a previous loading and unloading during multi-step nanoindentation experiments lower the stress required for further plastic deformation. In addition, the storage of partial dislocations also serves to render plastic flow to commence at lower stresses. This work provides new insights for the fabrication and property optimization of NG alloys.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl3 by Materials Project

Al3Li is Uranium Silicide structured and crystallizes in the cubic Pm-3m space group. The structure is three-dimensional. Li is bonded to twelve equivalent Al atoms to form LiAl12 cuboctahedra that share corners with twelve equivalent LiAl12 cuboctahedra, edges with twenty-four equivalent AlLi4Al8 cuboctahedra, faces with six equivalent LiAl12 cuboctahedra, and faces with twelve equivalent AlLi4Al8 cuboctahedra. All Li–Al bond lengths are 2.85 Å. Al is bonded to four equivalent Li and eight equivalent Al atoms to form distorted AlLi4Al8 cuboctahedra that share corners with twelve equivalent AlLi4Al8 cuboctahedra, edges with eight equivalent LiAl12 cuboctahedra, edges with sixteen equivalent AlLi4Al8 cuboctahedra, faces with four equivalent LiAl12 cuboctahedra, and faces with fourteen equivalent AlLi4Al8 cuboctahedra. All Al–Al bond lengths are 2.85 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Al2 by Materials Project

Al2Li3 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. there are two inequivalent Li sites. In the first Li site, Li is bonded in a 4-coordinate geometry to four equivalent Al atoms. There are three shorter (2.73 Å) and one longer (2.90 Å) Li–Al bond lengths. In the second Li site, Li is bonded in a distorted linear geometry to two equivalent Al atoms. Both Li–Al bond lengths are 2.81 Å. Al is bonded in a 8-coordinate geometry to five Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li9Al4 by Materials Project

Al4Li9 is zeta silver zinc-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are five inequivalent Li sites. In the first Li site, Li is bonded in a 2-coordinate geometry to two Al atoms. There are one shorter (2.79 Å) and one longer (2.83 Å) Li–Al bond lengths. In the second Li site, Li is bonded in a 4-coordinate geometry to four Al atoms. There are a spread of Li–Al bond distances ranging from 2.77–2.92 Å. In the third Li site, Li is bonded in a 2-coordinate geometry to two equivalent Al atoms. There are one shorter (2.76 Å) and one longer (2.91 Å) Li–Al bond lengths. In the fourth Li site, Li is bonded in a distorted linear geometry to two equivalent Al atoms. Both Li–Al bond lengths are 2.75 Å. In the fifth Li site, Li is bonded in a 3-coordinate geometry to three Al atoms. There are two shorter (2.71 Å) and one longer (2.85 Å) Li–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 8-coordinate geometry to six Li atoms. In the second Al site, Al is bonded in a 9-coordinate geometry to six Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li3Al by Materials Project

Li3Al is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. there are two inequivalent Li sites. In the first Li site, Li is bonded to eight Li and four equivalent Al atoms to form distorted LiLi8Al4 cuboctahedra that share corners with twelve equivalent LiLi8Al4 cuboctahedra, edges with eight equivalent LiLi8Al4 cuboctahedra, edges with eight equivalent AlLi12 cuboctahedra, faces with four equivalent AlLi12 cuboctahedra, and faces with ten equivalent LiLi8Al4 cuboctahedra. There are four shorter (2.77 Å) and four longer (2.94 Å) Li–Li bond lengths. All Li–Al bond lengths are 2.94 Å. In the second Li site, Li is bonded in a square co-planar geometry to eight equivalent Li and four equivalent Al atoms. All Li–Al bond lengths are 2.77 Å. Al is bonded to twelve Li atoms to form AlLi12 cuboctahedra that share corners with four equivalent AlLi12 cuboctahedra, edges with eight equivalent AlLi12 cuboctahedra, edges with sixteen equivalent LiLi8Al4 cuboctahedra, faces with four equivalent AlLi12 cuboctahedra, and faces with eight equivalent LiLi8Al4 cuboctahedra.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl3 by Materials Project

Al3Li is Uranium Silicide-like structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Li is bonded to twelve Al atoms to form LiAl12 cuboctahedra that share corners with four equivalent LiAl12 cuboctahedra, edges with eight equivalent LiAl12 cuboctahedra, edges with sixteen equivalent AlLi4Al8 cuboctahedra, faces with four equivalent LiAl12 cuboctahedra, and faces with eight equivalent AlLi4Al8 cuboctahedra. There are four shorter (2.83 Å) and eight longer (2.86 Å) Li–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to four equivalent Li and eight Al atoms to form distorted AlLi4Al8 cuboctahedra that share corners with twelve equivalent AlLi4Al8 cuboctahedra, edges with eight equivalent LiAl12 cuboctahedra, edges with eight equivalent AlLi4Al8 cuboctahedra, faces with four equivalent LiAl12 cuboctahedra, and faces with ten equivalent AlLi4Al8 cuboctahedra. There are four shorter (2.83 Å) and four longer (2.86 Å) Al–Al bond lengths. In the second Al site, Al is bonded in a distorted square co-planar geometry to four equivalent Li and eight equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Li2Al by Materials Project

Li2Al crystallizes in the orthorhombic Cmcm space group. The structure is two-dimensional and consists of two Li2Al sheets oriented in the (0, 1, 0) direction. there are two inequivalent Li sites. In the first Li site, Li is bonded in a 4-coordinate geometry to four equivalent Al atoms. There are two shorter (2.73 Å) and two longer (2.89 Å) Li–Al bond lengths. In the second Li site, Li is bonded in a 2-coordinate geometry to two equivalent Al atoms. Both Li–Al bond lengths are 2.81 Å. Al is bonded in a 9-coordinate geometry to six Li atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl by Materials Project

LiAl crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Li is bonded in a 11-coordinate geometry to four equivalent Li and seven Al atoms. There are one shorter (2.86 Å) and three longer (2.95 Å) Li–Li bond lengths. There are one shorter (2.87 Å) and six longer (2.95 Å) Li–Al bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to six equivalent Li and three equivalent Al atoms. All Al–Al bond lengths are 2.58 Å. In the second Al site, Al is bonded in a 11-coordinate geometry to eight equivalent Li and three equivalent Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on LiAl by Materials Project

LiAl crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are three inequivalent Li sites. In the first Li site, Li is bonded to four equivalent Al atoms to form distorted edge-sharing LiAl4 tetrahedra. There are two shorter (2.85 Å) and two longer (2.88 Å) Li–Al bond lengths. In the second Li site, Li is bonded in a 6-coordinate geometry to four Al atoms. There are two shorter (2.79 Å) and two longer (2.81 Å) Li–Al bond lengths. In the third Li site, Li is bonded in a 6-coordinate geometry to six Al atoms. There are a spread of Li–Al bond distances ranging from 2.77–2.98 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 9-coordinate geometry to four Li and five Al atoms. There are a spread of Al–Al bond distances ranging from 2.55–2.70 Å. In the second Al site, Al is bonded in a 5-coordinate geometry to five Li and two equivalent Al atoms.

36 MATERIALS SCIENCE↗