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(Color online) Schematic unit cell of the pyrite structure . Large balls represent Pt atoms and small balls the N atoms. Each octahedral interstitial of the Pt sublattice contains one dimer. The structure can also be regarded as a stacking of the corner-shared octahedra bonded with N-N connections.
Energy of as a function of the position of N atoms . When reduces to .
Band structure of , showing an indirect band gap. The band gap is 1.30 eV (GGA) or 1.77 eV (LDA).
Calculated total density of states (DOS) of . The valence band top locates at 0 eV.
The calculated structural parameters of . The space group is Pa3 (No. 205). Pt atoms occupy 4a sites and N atoms occupy 8b sites. There are only two free parameters, i.e., the lattice constant and the positional parameter of nitrogen atoms. The bulk modulus and its pressure dirivative are also given. In the experimental paper, (Ref. 1) two pressure derivatives were used, giving two bulk moduli.
The elastic stiffness constants , bulk modulus , shear modulus , Young’s modulus , and Poisson’s ratio of . All elastic constants except are in GPa.
The bond length , electron density , and Laplacian of at the BCPs of and diamond. Table shows GGA results.
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