Atomic and electronic structures of $4d$ transition-metal nitrides

A systematic theoretical study of the zinc-blende-type $4d$ transition-metal nitrides, which has not yet been synthesized, is performed in order to anticipate their electronic properties. Calculations were carried out by means of spin-polarized first-principles full-potential linearized augmented plane-wave calculations using the local spin-density approximation. Lattice constants, bulk moduli, cohesive and formation energies, charge distributions, energy band structures, and density of states are reported, and trends are discussed.

Figure 1

The equilibrium lattice constants (a) and bulk moduli (b) of zinc-blende-type structure $4d$ transiton-metal nitrides.

Figure 2

(Color online) The equilibrium lattice constants (a) and bulk moduli (b) for the pure transition metal in the fcc phase (Ref. 42).

Figure 3

(Color online) The bulk moduli values as a function of the first-neighbor distance of zinc-blende-type structure $4d$ transition-metal nitrides.

Figure 4

(Color online) Cohesive energies $E_{\mathit{coh}}^{\left(4d\text{−}\mathit{TM}\right)\mathrm{N}}$ of the $\left(4d\text{−}\mathrm{TM}\right)\mathrm{N}$ in the zinc-blende phase compared to the calculated values for NaCl phase and for the fcc phase of the pure metals, $E_{\mathit{coh}}^{\mathit{TM}}$ (a) Ref. 20, (b) Ref. 42. Also shown is the binding energy of the ${\mathrm{N}}_2$ molecule $E_{\mathit{bin}}$ (c) Ref. 50.

Figure 5

Formation energies of the $\left(4d\text{−}\mathrm{TM}\right)\mathrm{N}$, in the zinc-blende phase (circles), compared to the calculated ones in Ref. 21 for NaCl phase (squares).

Figure 6

Band structure for zinc-blende $4d$ transition-metal nitrides at the LDA minimum total energy. The horizontal line denotes the position of the Fermi energy.

Figure 7

(Color online) Characteristic band separations and bandwidths.

Figure 8

Total and partial density of states for the zinc-blende $4d$ transition-metal nitrides at the LDA minimum total energy. The vertical line denotes the position of the Fermi energy. The ligand states are denoted by L, antiligand by aL, and nonligand by nL.

Figure 9

Partial density of states for $4d\left(e\right)$-TM, $4d\left(t_2\right)$-TM, and $2p\text{−}\mathrm{N}$. The vertical line denotes the position of the Fermi energy. The ligand states are denoted by L, antiligand by aL, and nonligand by nL.

Figure 10

(Color online) The density of states $\rho \left(E_F\right)$ at the Fermi energy, and Stoner’s enhancement parameter $S_F$.