Vibrational and structural properties of <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi mathvariant="normal">P</mml:mi><mml:mn>2</mml:mn></mml:msub><mml:msub><mml:mi mathvariant="normal">O</mml:mi><mml:mn>5</mml:mn></mml:msub></mml:math> glass: Advances from a combined modeling approach

We present experimental measurements and ab initio simulations of the crystalline and amorphous phasesof P2O5. The calculated Raman, infrared, and vibrational density of states (VDOS) spectra are in excellentagreement with experimental measurements and contain the signatures of all the peculiar local structures of theamorphous phase, namely, bridging and nonbridging (double-bonded or terminal) oxygens and tetrahedral PO4units associated with Q2, Q3, and Q4 species (Qn denotes the various types of PO4 tetrahedra, with n beingthe number of bridging oxygen atoms that connect the tetrahedra to the rest of the network). In order to revealthe internal structure of the vibrational spectrum, the characteristics of vibrational modes in different frequencyranges are investigated using a mode-projection approach at different symmetries based on the Td symmetrygroup. In particular, the VDOS spectrum in the range from ∼600 to 870 cm−1 is dominated by bending (F2b)motions related to bridging oxygen and phosphorus (∼800 cm−1 band) atoms, while the high-frequency doubletzone (∼870–1250 cm−1) is associated mostly with the asymmetric (F2s) and symmetric (A1) stretching modes,and most prominent peak around 1400 cm−1 (exp. 1380 cm−1) is mainly due to asymmetric stretching vibrationssupported by double-bonded oxygen atoms. The lower-frequency range below 600 cm−1 is shown to arise froma mixture of bending (E and F2b) and rotation (F1) modes. The scissors bending (E) and rotation (F1) modes arewell localized below 600 cm−1, whereas the F2b bending modes spread further into the range ∼600–870 cm−1.The projections of the eigenmodes onto Q2, Q3, and Q4 species yield well-defined contributions at frequenciesin striking correspondence with the positions of the Raman and infrared bands.

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