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#eq    a    -1
1 box  Al  0 0 0 / 0 0 -1   3 3 1
2 box  Fe  0 0 0 / 0 0 ~a  = = =
3 box  Fe  0 0 0 / 0 0 ~a  = = 1.5 
4 box  Fe  0 0 0 / 0 0 ~a  = = 2
5 box_w sp 0 0 0 / 0 0 0
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