Abstract
Ion-acoustic structures in electron–positron–ion (e-p-i) plasma are examined by algebraic analysis of model equations. The dynamic of solitary waves are studied through direct approach. The system energy is obtained in terms of velocity of ions. It is founded that, ion-acoustic solitary waves existence are sensitive to densities and temperatures ratio of electrons and positrons. A small but finite amplitude approximation for soliton and shock waves are studied. The effect of positron parameters on solitonic wave and shocks are also inspected.