Amorphous AlB2, AlBC, and AlBN alloys: A first-principles study

First-principles molecular dynamics simulations were used to generate the samples of amorphous a-AlB2, a-AlBC and a-AlBN alloys. All alloys exhibit boron clustering. The Al-C network of a-AlBC shows some similarity to the structure of the Al4C3 phase however noticeable segregation of this phase is not identified. In a-AlBN, a small segregation of nanoscale w-AlN-like domains was revealed. The phonon spectra of the amorphous samples consist of one broad band spreading up to 39 THz. Hardness, ideal tensile strength, Debye temperature, and fracture toughness of the alloys are in the range 7.1-9.1 GPa, 9.2-20.1 GPa, 745-789 K and 1.43-1.46 mPa m1/2, respectively. Crystalline AlB2 is predicted to be closer to a brittle material, whereas the amorphous alloys will exhibit ductile behavior. All the amorphous samples should exhibit semiconducting properties with a predicted mobility gap in the range of 1.52-3.03 eV.