Molecular dynamics simulation of lattice structure, radiation damage, and vibrational spectra of zircon (ZrSiO4).

Liu, G. K. ; Zhuang, H. Z. ; Beitz, J. V.

Technical Information Center Oak Ridge Tennessee

关键词: Zircon;    Crystal lattices;    Molecular dynamics method;    Radiation effects;    Absorption spectra;   

RP-ID  :  DE2001768604

学科分类：工程和技术（综合）

美国|英语

来源: National Technical Reports Library

【 摘 要 】

The lattice structure, phonon density of states, and infrared spectrum for crystalline zircon, ZrSiO(sub 4), have been studied using a molecular dynamics (MD) simulation method that utilizes the Born-Mayer-Huggins and Coulomb pair potentials and the Stillinger-Weber three-body potential. A lattice block of ZrSiO(sub 4), which contains 343 unit cells with dimensions of 4.6249 x 4.6249 x 4.1874 nm(sub 3) and containing 8232 ions, was considered in our calculations. The simulated lattice structure agreed with that determined from x-ray and neutron diffraction experiments. The vibrational modes and absorption spectrum were calculated based on the simulated lattice and compared with infrared absorption spectra. Characteristic lines in infrared spectra obtained from previous experiments on natural and synthetic zircon were assigned to specific bond structures by interactive MD simulations with variation of selected potential parameters. It is shown that the O-Si-O three-body correlations in the SiO(sub 4) tetrahedron significantly influence the spectrum. It is demonstrated that the oxygen ions that are parallel and perpendicular to the c-axis in the SiO(sub 4) tetrahedron are inequivalent and make different contributions to the vibration spectrum. The energy distribution among 24 atoms in a unit cell in the 1011-cm(sup (minus)1) vibrational mode is shown in Fig. 1. Comparison between the simulated infrared absorption spectrum and that from experiments on synthetic zircon is shown in Fig. 2. The interactive method of fitting simulated results to those determined from experiments may be used as a tool for studying nanostructure and thermodynamics properties of materials. The model potentials for the ZrSiO(sub 4) lattice are refined and further applied to MD simulation of lattice disordering and line broadening that are induced by radiation damage processes and amorphization. We have further simulated alpha-decay-induced damage and dynamical recovery in the lattice of ZrSiO(sub 4). The simulated lattice with structure damage is used for reproducing infrared spectra that were obtained from radiation-damaged samples. The mechanisms and microscopic behavior of lattice disordering and dynamical recovery will be discussed.