[Pw_forum] propagation direction in the input file for dynmat.x

[Li YL]

Dear all users, 

Now I've a question on the polar materials. In order to get LO-TO splitting, you know, we need to use dynmat.x. In the input file for dynmat.x, we need input q(1), q(2), and q(3), that is, the propagation direction. I don't know how to choose this direction. My system has hexagonal symmetry and its primitive cell is rhombohedral. 
Any suggestions are welcome. Thanks in advance. 

Bests, 

Yanling Li, 

Institute of Solid states physics, CAS, P. R. China. 

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