Theoretical Studies on the F‐Centre in Alkali Halides

Abstract

The results of the theoretical study of I he electronic states of the R+-centre in alkali halides are reported. No empirical parameters are used in this calculation. The electronic core polarization is taken into account. The results of the calculation are in satisfactory agreement with the experimental data and can be considered as a theoretical confirmation of the F;-model of the R+-centre. B pa6o~e M~J I~~~I O T C I Ipe3ynt~a~h1 TeopeTmecKoro paccMoTpeHm a n e~~p o r r -HOB CTpymyphi R+ UeHTpa R uenoworanonzHbx KpneTannax. Hmamie 3~nl1-pwecmie napaMeTpbr B pacseTe IIe ~c n o n i~i y m~c~~. YVsaTbIsaercR s n e~~p o~r r a n IlOJl~~l43aIWIJI HOHOB OCTOBa. Pe3YJIbTaTbI PaCveTa y~OBJIeTBOpHTe~bI10 COrJlaCyIOTCH C 3IiC~ePHMelITaJ1hIIhIMIl AaHHbIMH H MorYT paCCMaTpnBaThCH HBK TeOpeTH9ecKoe IIoATBepXHeHHe F:-ivoaenm R ' -l i e~~p a . Model of the R+-CentreUnder X-ray irradiation and exposure to light of appropriate frequency the F-aggregate centres in alkali halides can be ionized. I n this process charged centres (FZ, F3+) are generated from neutral aggregate centres (F2, F3) All these results give support for choosing as model of the Rf-centre a n aggregate of three adjacent negative-ion vacancies with two electrons localized on them.which the transition t>akes place ;

Optical absorption of FAcentres in mixed ionic crystals

“…Weber and Dick [5] also found that the empirical factor cy = 0.53 gave absorption splitting in the wrong direction and, when they set cy = 1, qualitative agreement with experiment was obtained. Evarestov [6] obtained similar results for KC1 : Na. Ong and Vail [7] and Ong [8] have further used the lattice static method to include the non-harmonic displacement of the impurity ions in FA and FB centres.…”

Calculations of the Electronic Structure of Colour Centres in Ionic Crystals (II)

“…This colour centre (ionized R-centre) was considered in [32]. The wave functions for the ground state lAlg and for the first excited state 1E were taken in the following form:…”

Calculations of Optical Transitions of the F Center

“…Theoretically the Fsf center has been studied, earlier, by Wang [13] and by Evarestov and Treiger [14]. Wang used a semicontinuum model to compute the Fz transition energy in KC1.…”