Boron-rich crystals in A1-M-B (M = Li, Be, Mg) systems grown from high-temperature aluminum solutions

Fracture Strength ofAlLiB14

“…The calculated lattice parameters for AlLiB 14 are 5.88, 10.39, and 8.15Å, which agree well with the reported experimental values 5.847, 10.354, and 8.143Å. [18] The ideal brittle cleavage model used here separates the AlLiB 14 crystal into two semi-infinite, rigid atomic blocks that are pulled apart to introduce a pair of cleavage surfaces at a predefined atomic plane. This idealized approach simultaneously stretches and breaks all the bonds at the interface.…”

“…The physical features of fracture neglected in this ideal brittle cleavage model, including crack tip plasticity, lattice contractions, and atomic reconstructions, results in an overestimation of the cleavage energy and subsequently the actual critical energy and stress will be lower than our calculated results. The experimentally measured hardness for AlLiB 14 ranges between 20 and 29 GPa [18,21], which suggests that for this material the atomic scale behavior that we have reported here plays an important role in determining the actual hardness of the material. In summary, we have coupled the results from a series of ideal brittle cleavage strength calculations to the calculated orientation dependent Young's modulus to predict the fracture strength of AlLiB 14 .…”

“…[13][14][15]20] This is in part because the system is known to accept a large number of metal species including Li, Be, Na, Mg, Al, as well as a variety of rare-earth elements, such as Tb, Dy, Ho, Er, Yb, and Lu. [4,18,19,[21][22][23][24] In addition the superhard Ames Lab specimen was synthesized by a mechanical alloying method, which introduces a wide variety of impurity species to the crystal including Ti, Si, Fe, O, and C. [5] In these theoretical studies the reported figure of merit for hardness is the bulk modulus because its computation is relatively simple. However, the bulk modulus alone only gives information about the average bond strength under an applied volume dilation and does not give any information about the strength of individual bonds in the crystal.…”

Bonding and elastic properties of amorphous AlYB

“…Similar values were calculated for AlMgB 14 and (Al,Si) MgB 14 [9,10]. Hardness values in the range of 30 GPa were measured for AlLiB 14 [4]. With the addition of TiB 2 to AlMgB 14 hardness values up to 46 GPa were reported [11].…”

“…Many compounds are known, such as AlMgB 14 , AlNaB 14 , AlLiB 14 , AlYB 14 , AlTbB 14 , AlDyB 14 , AlHoB 14 , AlErB 14 , AlYbB 14 and AlLuB 14 [1][2][3][4][5]. Bulk modulus of AlMgB 14 was measured to be in the range of 196-264 GPa [6].…”