Computational modelling of intrinsic defects in the orthosilicates Y₂SiO₅ and Lu₂SiO₅

Abstract

Atomistic computer modelling techniques were applied to study the intrinsic defects in the Y2SiO5 (YSO) and Lu2SiO5 (LSO) structures at 0 and 300 K temperatures. The approach used is based on the interatomic potentials model and lattice energy minimization. A set of potential parameters were obtained by empirical adjustment and reproduced the lattice parameters with values better than 0.98% and 2.24% for YSO and LSO, respectively. Intrinsic defects were performed using the well-known Mott-Littleton method. Two conditions were adopted to calculate defects: for unbonded condition, point defects (vacancies and interstitials) were calculated without possible interactions with each other; for bounded condition, point defects interact with each other through coulomb and short-range potentials. All possible configurations were tested for Frenkel and Schottky defects in unbounded condition and only the most favourable defect configuration was considered in bounded condition. Oxygen Frenkel type is the most favourable energetic defect in both structures at both temperatures. Bounded defects calculations showed that oxygen vacancy and interstitial located in first coordinate sphere have the lowest solution energy values for LSO. However, the most favourable defect positions are further apart in the YSO structure. The bounded condition was most favourable decreasing the energetic costs of the defect for all cases demonstrating that the interaction of O Frenkel pair should be consider in future works.

Theoretical investigation of formation and diffusion mechanisms for point defects in ytterbium and lutetium silicates

“…Namely, the O Frenkel pairs are the predominant defect complexes in RE 2 SiO 5 . This conclusion is consistent with the previous work 50 …”

“…This conclusion is consistent with the previous work. 50 The defect concentration C d is calculated using the defect formation energy through Arrhenius formula as: where, N site and N config represent the number of sites in per unit cell or lattice cell or supercell and that of equivalent defective configurations, respectively. E f is the formation energy of each defect complex.…”

Effect of trivalent rare earth doping in cadmium silicates hosts: a theoretical study

“…The set of potential parameters used is based on two interatomic potentials (Buckingham and three body) plus shell model for oxygen ion polarisation. Such potential parameters were previously published in the references [16,20,25]. These sets of interatomic potentials were obtained by fitting the potential parameters to the CdSiO 3 , Cd 2 SiO 4 and Cd 3 SiO 5 structures as well as their CdO and SiO 2 precursor oxides [16].…”

“…These sets of interatomic potentials were obtained by fitting the potential parameters to the CdSiO 3 , Cd 2 SiO 4 and Cd 3 SiO 5 structures as well as their CdO and SiO 2 precursor oxides [16]. The set of potential parameters for all rare Earth oxides (R 2 O 3 ) was obtained from [20,25] to describe the doping ions.…”

“…In this work, we will use classical atomistic computer modelling to conduct a theoretical study of the cadmium silicate family doped with trivalent R ions. This doping study is based on previous works on other materials which provided an understanding about defects from the point of view of formation, structure distortions and energetic aspects [20][21][22][23][24][25].…”