Raman and infrared phonons in tetragonal ZnP₂and CdP₂crystals: a density functional study

Area of Science:

• Solid State Physics
• Materials Science
• Computational Chemistry

Background:

• Zinc phosphide (ZnP2) and cadmium phosphide (CdP2) are compounds with complex crystal structures.
• Understanding their lattice dynamics is crucial for predicting material properties and applications.

Purpose of the Study:

• To investigate the lattice dynamic properties of tetragonal ZnP2 and CdP2 crystals.
• To assign specific lattice eigenmodes to experimentally observed Raman and infrared active modes.
• To elucidate the contribution of phosphorus spiraling chains to the vibrational spectra.

Main Methods:

• Density Functional Theory (DFT) calculations were employed.
• Theoretical vibrational spectra were computed.
• Comparison with experimental Raman scattering and infrared spectroscopy data was performed.

Main Results:

• Calculated lattice dynamic properties show good agreement with experimental Raman and infrared data.
• Raman- and infrared-active modes were successfully assigned to specific lattice eigenmodes.
• Distinct features in the vibrational spectra were attributed to the presence of four spiraling phosphorus chains per unit cell.

Conclusions:

• The DFT approach accurately predicts the lattice dynamics of ZnP2 and CdP2.
• The unique crystal structure, specifically the phosphorus spiraling chains, significantly influences the vibrational properties.
• This work provides a foundation for further research into phosphide materials.