TE-125 NMR IN TEO2 SINGLE-CRYSTAL - TE-TE CHEMICAL BONDING AND TUNNELING OF 5S(2) ELECTRONS

The Te-O and Te-Te bonds in TeO2, have been studied from Te-125 NMR si ngle crystal data. The Te-125 NMR chemical shift tensor has principal components delta(11) = 727.5, delta(22) = 1586.2 and delta(33) = 2065. 8 ppm. The Te-125 magnetic shielding tensor is represented as a sum of constituents characterising the off-ionic parts of the separated Te-T e and Te-O interactions. It is shown that the Te-Te exchange interacti on is associated with a strong polarization of the Te4+ ion under the intramolecular electric field and with tunneling of 5s(2) electrons al ong the Te-Te bonds. (C) 1998 Elsevier Science B.V.