Born Effective Charges and Infrared Response of LiBC

Abstract

Calculations of the zone center optical mode frequencies (including LO-TO splitting), Born effective charges Z${}_{\alpha \alpha }^{\ast }$ for each atom, dielectric constants ${\epsilon }_0$ and ${\epsilon }_{\infty }$, and the dielectric response in the infrared, using density functional linear response theory, are reported. Calculated Raman modes are in excellent agreement with experimental values (170 cm${}^{-1}$ and 1170 cm${}^{-1}$), while it will require better experimental data to clarify the infrared active mode frequencies. The Born effective charges Z${}_{\alpha \alpha }^{\ast }$ (i) have surprisingly different values for B and C, and (ii) show considerable anisotropy. Relationships between the effective charges and LO-TO splitting are discussed, and the predicted reflectivity in the range 0 -- 1400 cm${}^{-1}$ is presented. These results hold possible implications for Li removal in LiBC, and C substition for B in MgB${}_2$.

6 pages, 3 figures

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• Comparison of the Electronic Structures of Two Non-cuprate Layered Transition Metal Oxide Superconductors
• Anisotropy in the dielectric function of Bi${}_2$Te${}_3$ from first principles: From the UV-visible to the infrared range
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