[Pw_forum] Supercell with sides not parallel to lattice vectors

[Amar Singh]

Dear Friends,​I have a rhombohedral unit cell of ten atoms (two molecules per cell). I want to form a supercell of this structure having 40 atoms, but its sides are not be parallel to the lattice vectors of original unit cell. My first impression is that I can't use the original lattice parameters for optimizing this supercell, as I saw in many QE examples, please correct me if I am wrong. I can think of two possibilities -  ​1. Considering this unit of 40 atoms being in a triclinic unit cell (ibrav = 14) could be a option, and I can use positions of the atoms in Angstroms. Though I will surely loose the opportunity to set the space group if I use this method.​2. If I give the space group and lattice parameters of 40 atom supercell (without mentioning ibrav) with the positions of atoms in angstroms/crystal_sg, will this work ?​Please suggest me which of them makes more sense, and if there could be a better alternative to both of them ? Thanks​Amar 
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