[CST] simulation for SRR structures

i'm a beginner working on SRR structures and trying to recover the simulation results provided by the literature.
i also browsed the discussions on PBG/EBG simulation in CST in the forum, launched by pushhead, shahid78, etc.
i'd like to make these questions clear here very much:
1. when should the "unit cell" and "periodic" be applied, when it comes to the boundary condition. what's the difference between them?
2. when we simulate the array structure formed by the SRR unit (e.g 5*5 array), is using a wave port with Et=0 at the bottom and top walls and Ht=0 at the left and right walls equivalent to applying a plane wave excitation with the corresponding E and H directions? then how about the other two walls--set to be open? it seems so according to what eckypting mentioned in the previous discussion, but i'm not sure whether i've got it properly.
3. then it finally falls to the current simulation i'm busy with. why i cannot get the result as the paper shows, following the boundary settings it mentions--"Our simulations used periodic boundary conditions on the transverse boundaries and two open ports to simulate the S-parameter amplitudes (reflection and transmission) of SRR".
Could someone help check the model(in the attached) for me?
i'm looking 4ward to ur comments and thank you very much!

HI DrunkBear,
it seem that its quite some time passed after the question that u posted here.
I am working on SRR structure recently.May i know whether u have completed what u research on?