  This paper presents an analytical pathloss model for reconfigurable
intelligent surface (RIS) assisted terahertz (THz) wireless systems.
Specifically, the model accommodates both the THz link and the RIS
particularities. Finally, we derive a closed-form expression that returns the
optimal phase shifting of each RIS reflection unit. The derived pathloss model
is validated through extensive electromagnetic simulations and is expected to
play a key role in the design of RIS-assisted THz wireless systems.
