[Pw_forum] A question about PWscf

[pzc at sjtu.edu.cn]

Hello,
   I am a graduate student in Shanghai Jiaotong University. We are taking ab inito calculations now. And we need some information about your PWscf. In this software, how to constrain a relaxation to relax only in x,y direction and fix z direction unchanged? What parameters should be used in the input file?  
   Hope your respond, many thanks!               
                                      Panzic 22 Aug 2004