[Pw_forum] A method on defining a based-centered monoclinic cell

[yinwei_li]

Dear Pwscf users, 

    Recently I found an effective way on input defining a based-centered monoclinic cell.

In fact, we could  change the setting (ibrav=13) in the flib/latgen.f90 from 
     sen = sqrt( 1.d0 - celldm(4) ** 2 )
     a1(1) = 0.5 * celldm(1)
     a1(3) =-a1(1) * celldm(3)
     a2(1) = celldm(1) * celldm(2) * celldm(4)
     a2(2) = celldm(1) * celldm(2) * sen
     a3(1) = a1(1)
     a3(3) =-a1(3)

to 

     sen = sqrt( 1.d0 - celldm(4) ** 2 )
     a1(2) = 0.5 * celldm(1)
     a1(3) =-0.5 * celldm(2) * celldm(1)
     a2(2) = 0.5 * celldm(1)
     a2(3) = 0.5 * celldm(2) * celldm(1)
     a3(1) = celldm(3) * sen * celldm(1)
     a3(2) = celldm(3) * celldm(4) * celldm(1)

which corresponding with the defining form in the MS. 

I have tested it and found this way of defining could give us a right structure.

For some stuctures which have problems in input defining the cell, I think we could resolve it in the same way 
"change the defining form in latgen.f90 to a new one which corresponding with that in the MS"

Good Luck!

Yinwei Li2009-


Y03-07 body centered tetragonal 



     sen = sqrt( 1.d0 - celldm(4) ** 2 )
     a1(1) = 0.5 * celldm(1)
     a1(3) =-a1(1) * celldm(3)
     a2(1) = celldm(1) * celldm(2) * celldm(4)
     a2(2) = celldm(1) * celldm(2) * sen
     a3(1) = a1(1)
     a3(3) =-a1(3)
yinwei_li 
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