An additive semi-implicit Runge-Kutta family of schemes for nonstiff systems

An additive semi-implicit third-order Runge-Kutta family of schemes for nonstiff systems of equations is presented. These schemes involve a single implicit stage and two explicit stages and posses a linear stability domain that is larger than that of explicit Runge-Kutta schemes of the same order. The improved stability domain can be useful in some problems involving large systems of equations where a few components impose too stringent time-step limitations.