Driven by the Beam Energy Scan (BES) program at the RHIC, researches and discussions on the QCD phase diagram have flourished recently. In order to provide a reference from microscopic transport models, we performed a systematic analysis, using a multiphase transport (AMPT) model for the particle yields and a statistical model (thermus) for the thermal fit, for Au + Au collisions at sNN=7.7–200 GeV. It is found that at a fixed collision centrality the chemical freeze-out parameter, temperature Tch, increases with collision energy and somehow...
