Phonon spectra of eulytite crystals Bi4M3O12 (M = Ge,Si): ab initio study |
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| Affiliation: | 1. Department of Physics, West University of Timisoara, V. Parvan 4, Timisoara, 300223, Romania;2. Academy of Romanian Scientists, Independentei Street 54, Bucharest, 050094, Romania;3. Ural Federal University, 620002, Yekaterinburg, Russia;4. Shumen University “Konstantin Preslavsky”, 115 Universitetska Street, 9712, Shumen, Bulgaria;1. Vinča Institute of Nuclear Sciences, University of Belgrade, P.O. Box 522, 11001, Serbia;2. Institute of Solid State Physics, University of Latvia, 8 Kengaraga Street, Riga, LV-1063, Latvia;1. Department of Physics, University of the Free State-Qwaqwa Campus, Private Bag X13, Phuthaditjhaba, 9866, South Africa;2. Modibbo Adama University of Technology Yola, Nigeria;3. PSL Research University, Chimie ParisTech – CNRS, Institut de Recherche de Chimie Paris, 75005 Paris, France;1. Instituto de Química, UNESP, Rua Professor Francisco Degni, 55, 14800-900, Araraquara, SP, Brazil;2. Synchrotron SOLEIL, L’Orme des Merisiers, BP48, Saint Aubin, 91192, Gif-sur Yvette, France;1. IFN – CNR CSMFO Lab. & FBK CMM, via alla Cascata 56/C Povo, 38123, Trento, Italy;2. Politecnico di Milano, Dipartimento di Fisica and IFN-CNR, Piazza Leonardo da Vinci 32, 20133, Milano, Italy;3. Center for Nano Science and Technology@PoliMi, Istituto Italiano di Tecnologia, Via Giovanni Pascoli, 70/3, 20133, Milan, Italy;4. Dipartimento di Fisica, Università di Trento, via Sommarive 14, Povo, 38123, Trento, Italy;5. School of Physics, University of Hyderabad, Hyderabad, 500046, India;6. CSIRO Manufacturing Flagship, Ian Wark Laboratory, 3168, Clayton, Australia;7. Institute of Low Temperature and Structure Research, PAS, 2 Okolna St., 50-422, Wroclaw, Poland;8. Ruđer Bošković Institute, Division of Materials Physics, Laboratory for Molecular Physics, Bijenička c. 54, Zagreb, Davor, Croatia;9. Center of Excellence for Advanced Materials and Sensing Devices, Research Unit New Functional Materials, Bijenička c. 54, Zagreb, Croatia;10. Departamento de Química, Faculdade de Filosofia, Ciências e Letras de Ribeirão Preto, Universidade de São Paulo, Av. Bandeirantes, 3900, CEP 14040-901, Ribeirão Preto, SP, Brazil;11. College of Engineering, Swansea University, Singleton Park, Swansea, UK;12. Centro di Studi e Ricerche Enrico Fermi, P.zza Viminale 1, 00184, Roma, Italy;13. IFAC – CNR, MiPLab, Via Madonna del Piano 10, 50019, Sesto Fiorentino, Italy;14. IFN – CNR and Politecnico di Milano, Dipartimento di Fisica, Piazza Leonardo da Vinci 32, 20133, Milano, Italy;15. Dipartimento di Ingegneria Industriale, Università di Padova, via Marzolo 9, 35122, Padova, Italy;1. LumiLab, Department of Solid State Sciences, Ghent University, Belgium;2. Center for Nano- and Biophotonics (NB Photonics), Ghent University, Belgium |
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| Abstract: | 
In this paper we present the results of ab initio DFT calculation of phonon spectra for bismuth ortho-germanate Bi4Ge3O12 and bismuth ortho-silicate Bi4Si3O12 crystals, in the center of the first Brillouin zone. First, the geometry optimization was performed using the analytical energy gradients, with respect to atomic coordinates and unit cell parameters. Vibrational frequencies and normal modes were calculated within the harmonic approximation by diagonalizing the mass-weighted Hessian matrix. The IR and Raman spectra of both crystals were simulated with the periodic ab initio Crystal 09 code and B3LYP hybrid functional and the two sets of Transverse-Optical and Longitudinal-Optical frequencies are generated, together with their intensities. Also, the influence of isotopic substitution for Bi, Ge and O in phonon modes and the picture with values of frequencies shift in each mode by isotopic substitution were calculated. The obtained results are discussed and the comparision between the computed spectra and experimental data is quite satisfactory, which justifies the model and simulation scheme used for the title systems. |
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| Keywords: | BGO BSO Abinitio calculation Phonon spectra Isotopic shift |
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