First-principles lattice dynamics of NaCoO2

Article

关键词: FUNCTIONAL PERTURBATION-THEORY;    CONJUGATE-GRADIENT ALGORITHM;    TOTAL-ENERGY CALCULATIONS;    TRIANGULAR LATTICE;    NAXCOO2-CENTER-DOT-YH(2)O;    SUPERCONDUCTIVITY;    PSEUDOPOTENTIALS;    LAYERS;    MODEL;   

DOI  :  10.1103/PhysRevB.70.144518

来源: SCIE

【 摘 要 】

We report first-principles linear response calculations on NaCoO2. Phonon frequencies and eigenvectors are obtained throughout the Brillouin zone for two geometries with different Na site occupancies. While most of the phonon modes are found to be insensitive to the Na site occupancy, there are two modes dominated by out-of-plane vibrations of Na giving very different frequencies for different geometries. One of these two modes, the A(2u) mode, is infrared-active, and can be used as a suitable sensor of Na distribution/ordering. The longitudinal-transverse splitting of the zone-center optical-mode frequencies, Born effective charges, dielectric constants, and the infrared dielectric response are also reported, showing considerable anisotropy. The calculated frequencies of Raman-active modes generally agree with the experimental values of corresponding Na de-intercalated and/or hydrated compounds, while it requires better experimental data to clarify the infrared-active mode frequencies

【 授权许可】

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