Estimates of point defect production inα-quartz using molecular dynamics simulations

Abstract

Molecular dynamics (MD) simulations are performed to investigate the production of point defects in α-quartz by oxygen and silicon primary knock-on atoms (PKAs) of 0.25–2 keV. The Wigner–Seitz (WS) defect analysis is used to identify the produced vacancies, interstitials, and antisites, and the coordination defect analysis is used to identify the under and over-coordinated oxygen and silicon atoms. The defects at the end of the ballistic phase and the residual defects, after annealing, increase with increased PKA energy, and are statistically the same for the oxygen and silicon PKAs. The WS defect analysis results show that the numbers of the oxygen vacancies and interstitials (VO, Oi) at the end of the ballistic phase is the highest, followed closely by those of the silicon vacancies and interstitials (VSi, Sii). The number of the residual oxygen and silicon vacancies and interstitials are statistically the same. In addition, the under-coordinated OI and SiIII, which are the primary defects during the ballistic phase, have high annealing efficiencies (>89%). The over-coordinated defects of OIII and SiV, which are not nearly as abundant in the ballistic phase, have much lower annealing efficiencies (<63%) that decrease with increased PKA energy.

Characterization of radiation damage in TiO2 using molecular dynamics simulations

“…The accuracy of this potential has been confirmed in prior work [52,56]. Results showed that the lattice and elastic constants, density, equations of state, as a function of temperature and pressure, and energies of defect formation are in good agreement with reported experimental results by others [52,56]. A limitation of the ionic potentials, such as one used in this present work, is overestimating the melting point.…”

“…This potential gives displacement probability distributions that are nearly identical to those reported using a splined Buckingham-ZBL potential [52]. The accuracy of this potential has been confirmed in prior work [52,56]. Results showed that the lattice and elastic constants, density, equations of state, as a function of temperature and pressure, and energies of defect formation are in good agreement with reported experimental results by others [52,56].…”

“…These simulations employ a fitted Pedone [56] interatomic potential to a repulsive term to account for the short interatomic distances of the atoms during irradiation. This potential gives displacement probability distributions that are nearly identical to those reported using a splined Buckingham-ZBL potential [52]. The accuracy of this potential has been confirmed in prior work [52,56].…”

“…These simulations can be used to investigate defect production, accumulation and annihilation, formation of defect clusters, and possible amorphization, as well as determine the threshold displacement energies . Some of the reported results of MD simulations include TDE estimates [8,32,52] defect production near grain boundaries [51], and potential amorphization [46,47,53] in TiO 2 . However, no studies have investigated the effects of the PKA type and temperature, on defect production and potential amorphization in TiO 2 with PKA energies up to 10 keV.…”

EPR study of new E′ centers in neutron-irradiated α-quartz

“…Among them only some hole-like paramagnetic defects associated with silicon vacancies have been fully investigated [19,20]. Full knowledge of the nature of defects and dynamic properties (e.g., radiation dose dependence and thermal stability) is necessary for theoretic simulations of the damage process in neutron-irradiated quartz structure [21][22][23]. Also radiation-induced defects in natural quartz are useful for dating [24] and mineral exploration [25,26].…”