Efficient ab initio quantum mechanical simulations of structural stability and vibrational properties of bulk, monolayer and ( n ,0) nanotubes: Yttrium sesquioxide Y 2 O 3

• Published in: Journal of Raman spectroscopy Vol. 51; no. 2; pp. 232 - 242
• Main Authors: Larbi, Tarek, El‐Kelany, Khaled E., Doll, Klaus, Amlouk, Mosbah
• Format: Journal Article
• Language: English
• Published: 01-02-2020
• ISSN: 0377-0486; 1097-4555
• DOI: 10.1002/jrs.5778

In this contribution, we report reliable ab initio quantum mechanical simulations of a variety of physical properties concerning yttrium sesquioxide (Y
2
O
3
) in different arrangements from the bulk, the monolayer (
h
‐Y
2
O
3
), to the (
n
,0) single‐walled nanotubes in the range from
n
= 6 to 32, for geometry optimization and vibrational properties. Structural parameters, phonon wavenumbers, infrared (IR) and Raman intensities, and elastic constants are computed via density functional theory (DFT/B3LYP) where the trend towards the (
h
‐Y
2
O
3
) monolayer for large nanotube radius is discussed. We firstly report combined experimental and computational studies on the structural and vibrational properties of the bulk Y
2
O
3
. Then, IR and Raman spectra of all arrangements are simulated via the coupled perturbed Hartree–Fock and Kohn–Sham (CPHF/KS) computational schemes. For the (
n
,0) Y
2
O
3
nanotube family, two sets of IR active phonon modes in the (200–400 cm
−1
) and (600–900 cm
−1
) ranges are determined. Both of them tend smoothly with different slope, towards the optical vibrational modes of the
h
‐Y
2
O
3
single layer. Three sets of active phonon bands are obtained in their Raman spectrum. The first one, in the 0–100 cm
−1
range contains two phonon modes, their vibration wavenumbers tend to zero at very large tube radius and are found to be connected to the elastic constants C
11
and C
66
of the
h
‐Y
2
O
3
monolayer as the 1D
→
2D transition is approached. The second one, in 200–400 cm
−1
range tends to the optical mode
E
′ (
ν
= 308 cm
−1
) of the monolayer. The third set, in the 600–900 cm
−1
range contains two active modes, their intensities tend to zero in the limit of large nanotube without change in their vibration wavenumbers.