  Here we report pressure effect on superconducting transition temperature (Tc)
of ReFeAsO0.85 (Re= Sm and Nd) system without fluorine doping. In-situ
measurements under high pressure showed that Tc of the two compounds decrease
monotonously over the pressure range investigated. The pressure coefficients
dTc/dP in SmFeAsO0.85 and Nd FeAsO0.85 were different, revealing the important
influence of the deformation in layers on Tc. Theoretical calculations
suggested that the electron density of states decrease with increasing
pressure, following the same trend of experimental data.
