Multiscale computational simulation of amorphous silicates' structural, dielectric, and vibrational spectroscopic properties
Martinez-Gonzalez, Jose Angel (Universitat Autònoma de Barcelona. Departament de Química)
Navarro-Ruiz, Javier (Universitat Autònoma de Barcelona. Departament de Química)
Rimola, Albert (Universitat Autònoma de Barcelona. Departament de Química)

Data:	2018
Resum:	Silicates are among the most abundant and important inorganic materials, not only in the Earth's crust, but also in the interstellar medium in the form of micro/nanoparticles or embedded in the matrices of comets, meteorites, and other asteroidal bodies. Although the crystalline phases of silicates are indeed present in nature, amorphous forms are also highly abundant. Here, we report a theoretical investigation of the structural, dielectric, and vibrational properties of the amorphous bulk for forsterite (MgSiO) as a silicate test case by a combined approach of classical molecular dynamics (MD) simulations for structure evolution and periodic quantum mechanical Density Functional Theory (DFT) calculations for electronic structure analysis. Using classical MD based on an empirical partial charge rigid ionic model within a melt-quenching scheme at different temperatures performed with the GULP 4. 0 code, amorphous bulk structures for MgSiO were generated using the crystalline phase as the initial guess. This has been done for bulk structures with three different unit cell sizes, adopting a super-cell approach; that is, 1 × 1 × 2, 2 × 1 × 2, and 2 × 2 × 2. The radial distribution functions indicated a good degree of amorphization of the structures. Periodic B3LYP-geometry optimizations performed with the CRYSTAL14 code on the generated amorphous systems were used to analyze their structure; to calculate their high-frequency dielectric constants (ε); and to simulate their IR, Raman, and reflectance spectra, which were compared with the experimental and theoretical crystalline MgSiO. The most significant changes of the physicochemical properties of the amorphous systems compared to the crystalline ones are presented and discussed (e. g. , larger deviations in the bond distances and angles, broadening of the IR bands, etc. ), which are consistent with their disordered nature. It is also shown that by increasing the unit cell size, the bulk structures present a larger degree of amorphization.
Ajuts:	Ministerio de Economía y Competitividad CTQ2014-60119-P Agencia Estatal de Investigación CTQ2017-89132-P Agència de Gestió d'Ajuts Universitaris i de Recerca 2014/SGR-482 Agència de Gestió d'Ajuts Universitaris i de Recerca 2017/SGR-1320 Ministerio de Economía y Competitividad CTQ2013-40347-ERC
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	DFT ; Periodic simulations ; Amorphous minerals ; Physicochemical properties ; Super-cell
Publicat a:	Minerals, Vol. 8, Issue 8 (August 2018) , art. 353, ISSN 2075-163X

DOI: 10.3390/min8080353

25 p, 5.8 MB

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