Jomar B. Amaral

Computer modelling of defect structure and rare earth doping in LiCaAlF6 and LiSrAlF6

This paper describes a computational study of the mixed metal fluorides LiCaAlF6 and LiSrAlF6, which have potential technological applications when doped with a range of elements, especially those from the rare earth series. Potentials are derived to represent the structure and properties of the undoped materials, then defect properties are calculated, and finally solution energies for rare earth elements are calculated, enabling preferred dopant sites and charge compensation mechanisms to be predicted.

Computer modelling of thorium doping in LiCaAlF6 and LiSrAlF6: application to the development of solid state optical frequency devices

This paper describes computer modelling of thorium doping in crystalline LiCaAlF(6) and LiSrAlF(6). The study has been motivated by the interest in using these materials as hosts for (229)Th nuclei, which are being investigated for use as frequency standards. The dopant sites and form of charge compensation are obtained; this information is essential for the further development and optimization of these devices.

Computer modelling of divalent, trivalent and tetravalent ion doping in LiCaAlF6 and LiSrAlF6

This paper describes a computational study of the mixed metal fluorides LiCaAlF6 and LiSrAlF6, doped with divalent (Pb2+, Co2+ and Ni2+), trivalent (Cr3+, Fe3+ and Y3+) and tetravalent (Si4+) ions. For each of the frameworks, all three cation sites were considered, as well as a range of charge compensation mechanisms. For the divalent dopants, substitution at the divalent host site is preferred, whilst for the trivalent dopants, Co3+ and Fe3+ prefer the Al3+ site, and Y3+ shows behaviour similar to the rare earths. Finally, it is found that Al3+ is the preferred site for substitution by Si4+ in both host frameworks.

Computer modelling of defects and dopants in mixed metal fluorides

This paper describes a computer modelling study of rare earth doping in the mixed metal fluorides LiCaAlF 6 , LiSrAlF 6 and LiYF 4 . All these materials have potential technological applications, providing the motivation to improve understanding of their defect chemistry; in particular the energetics of doping and the sites occupied by dopant ions. Computer modelling is used to calculate the effect of rare earth dopant concentration on the structure of LiYF 4 , and to predict the sites occupied by rare earth dopants and the corresponding form of charge compensation, in LiCaAlF 6 and LiSrAlF 6 .

Computer modelling of mixed metal fluorides for optical applications

This paper describes a new computational method for predicting the optical behaviour of doped inorganic materials. There is considerable interest in using inorganic materials in photonic devices, and in many cases, the optical properties of these materials depend on doping by ions such as those from the rare earth series. Among the inorganic materials of interest are the mixed metal fluorides (e.g. BaLiF(3), BaY(2)F(8), YLiF(4), LiCaAlF(6), LiSrAlF(6)), doped with trivalent rare earth ions. The paper describes the use of Mott-Littleton calculations to determine the optimum location for dopant ions, followed by crystal field calculations which make direct use of the output of the Mott-Littleton calculations to calculate the optical properties of the dopant ion taking into account its symmetry and the positions of the surrounding ions, including any vacancies or interstitial ions present by virtue of charge compensation. It is then possible to predict whether a given dopant ion at a particular site in a material will have favourable optical properties.