3.3. Electronic properties
To study the conductivity and bonding characteristics, we further studied the electronic properties of Ti3AlB2, Ti2ZrAlB2-1 and Ti2ZrAlB2-2. As is shown in Figure 3, the finite positive values of density of states near Fermi level shows that they all have good electrical conductivity. From the case of partial density of states, it can be seen the conductivity are mainly contributed by Ti-d and B-p electron orbitals for Ti3AlB2, and Ti-d, Zr-d and B-p electron orbitals for two Ti2ZrAlB2. For Ti3AlB2 and Ti2ZrAlB2-2, the similar shape of partial density of states for Ti-d and B-p electron near Fermi level means show there is strong orbital hybridization between these two types of electrons. And the shape of Ti-d and Zr-d orbitals are similar for Ti2ZrAlB2-2, it indicates that metal bonds can also be formed between Zr and Ti atoms. While for Ti2ZrAlB2-1, Zr atoms also participate in bonding, which reduces the similarity of PDOS between Ti and B atoms compared with Ti3AlB2 and Ti2ZrAlB2-2. It indicates the ionic bonds in Ti3AlB2 and Ti2ZrAlB2-2 are stronger than that in Ti2ZrAlB2-1, this is also consistent with the result of Poisson ratio discussed earlier.