1Institute for Solid State Physics and Optics, Wigner Research Centre for Physics, P.O. Box 49, Budapest H-1525, HungaryThe structure of Ge(20)Te(80), Ge(15)Cu(8)Te(77) and Ge(15)Cu(5)Te(80) glasses was investigated by diffraction techniques and extended X-ray absorption fine structure measurements. Large structural models were generated by fitting experimental data by the reverse Monte Carlo simulation technique. In Ge(20)Te(80) glass, both Ge and Te obey the 8 - N rule, and the structure is built up of GeTe(4) tetrahedra connected via Te-Te bonding or shared Te atoms connected to two Ge atoms. The coordination number of Te is significantly higher than 2 in Ge(15)Cu(8)Te(77). The average coordination number of Cu is 3.41 +/- 1 in this alloy. In Ge(15)Cu(5)Te(80) glass, Cu binds mostly to Te, while Cu-Cu bonding is significant in Ge(15)Cu(8)Te(77). (C) 2011 Elsevier Ltd. All rights reserved.