Before revision:  We consider the model and pricing formula for equity value and using it calculate expected default barrier , Then We provide pricing model and formula for defaultable corporate bonds with discrete coupons and consider its duration . The results can be used in duration analysis of bonds and credit risk management in corporate finance .
After revision:  We consider the model and pricing formula for equity value and using it calculate expected default barrier , Then We provide pricing model and formula for defaultable corporate bonds with discrete coupons and consider its duration and the effect of the government taxes .