Unveiling the infrared complex dielectric function of ilmenite CdTiO3

Optical phonon modes in 1:2 ordered trigonal Ba3MgNb2O9 perovskite: Synergy of both classical and quantum methods

“…As a result, the polar phonons of the inclusions can be extracted in an unpolarized form, that is, without designations of the symmetry species. In this situation, ab initio calculations have become a fundamental tool to interpret and assign the reflectance infrared spectra in materials obtained only in their polycrystalline form 29 …”

“…In this situation, ab initio calculations have become a fundamental tool to interpret and assign the reflectance infrared spectra in materials obtained only in their polycrystalline form. 29 Beyond the description of symmetry for each polar phonon mode, the DFT calculations also provide some useful information regarding the complex dielectric tensor in view of its value at low and high frequency domains, that is, the static (ε s ) with ionic contributions and the electronic (ε ∞ ) part, respectively. The calculation can discriminate the vibrational contribution (dielectric strength) to static dielectric tensor for each polar mode.…”

“…Besides, to our knowledge until now, literature does not provide any work concerning the force field studies on the optical modes at Γ‐point in 1:2 ordered trigonal Ba 3 MgNb 2 O 9 perovskites. Indeed, we already described the vibrational spectra in some compounds including NdAlO 3 , 27 CdTiO 3 , 28,29 Ba 2 MgWO 6 , 30 Ba 3 CaNb 2 O 9 , 31 Fe 2 TiO 5 , 32 and BiOBr 33 . We aim to combine both classical and quantum methodologies to get further insights into the optical phonon description in barium magnesium niobate, which is a promising material for microwave applications.…”

Lattice dynamics and spontaneous magnetodielectric effect in ilmenite CoTiO$_3$

“…Allelectron basis sets TZVP [37] for Co, 8-6411(31d)G [38] for Ti, and 8-411(1d)G [38] for O have been used according to Ref. [25]. The reciprocal space integration was performed by sampling the Brillouin zone with the 12 × 12 × 12 Pack-Monkhorst mesh.…”

“…But further intensive research of this promising material is inhibited by the lack of complete information about the phonon spectrum. It is worth noting that up to now, most experimental studies of the lattice dynamics of ATiO 3 materials with ilmenite structure were performed on the poly-and microcrystalline samples using unpolarized far infrared [20,21,22,23,24,25] and Raman [26,27,28,29,30,31,32,33] spectroscopy.…”