Superconvergent derivative recovery for the intermediate finite element family of the second type

In this work, a recovery technique for the inter-mediate finite element fam ily of the second type is proposed and analysed on a second-order elliptic model problem. It is shown that when the pollution error is properly contro lled, the convergence rate of the recovered gradient is two orders higher t han the optimal global rate on an interior subdomain where rectangular mesh es of regular type are applied. Some numerical results are provided to conf irm the theoretical findings.