Network connectivity and extended Se chains in the atomic structure of glassy GeSe4

In order to contribute to the ongoing debate on the atomic structure of Se-rich GexSe1−x glasses, we have studied the structure of glassy GeSe4 by first-principles molecular dynamics. The Perdew–Burke–Ernzerhof generalized gradient approximation has been employed. The nearest-neighbor Se environment is found to be compatible with the coexistence of a network of GeSe4 tetrahedra and Sen chains, thereby confirming previous Perdew–Wang results. When comparing PW and PBE results, changes are found in the Ge–Ge coordination environment and in the number of GeSe4 tetrahedra. In addition, very extended Sen chains (n > 3, up to n = 12) are present (PBE case).