An anomalous alloy: YxSi1−x

The structural and dynamical properties of the rare earth silicon amorphous alloy YxSi1−x for x=0.093 and 0.156 are studied via density functional-based molecular dynamics. The Si network forms cavities in which a Y3+ cation is entrapped. Its electrons are transferred to the Si network and are located in the dangling bonds of the Si atoms that line the Y cavities. This leads to the presence of low coordinated Si atoms that can be described as monovalent or divalent anions. For x=0.156, the cavities touch each other and share Si atoms that have two dangling bonds. The vibrational spectrum is similar to that of amorphous Si. However, yttrium doping induces a shoulder at 70 cm−1 and a pronounced peak at 180 cm−1 due to low coordinated Si.