Dear QE users and developers, I am trying to use the real space force constants file obtained from q2r.x to do some other calculations outside of QE. For this purpose, I am trying to understand the format of the force constants file. I am attaching a sample force constants file obtained by performing ph.x and q2r.x on bulk silicon with a 4 x 4 x 4 q-mesh.
In the 22nd line in the file, it says 1 1 1 1. I believe the first two 1's denote the x-direction and the last two 1's denote atom numbers within the two-atom unit cell of silicon. After this it loops over all 64 different combinations of indices in a 4 x 4 x 4 mesh and lists the force constants in the 4th column. What do these 64 different combinations mean? Do they denote unit cells? For instance, let's take the first line: 1 1 1 2.6997. 2.6997 is the force constant between which atoms? Thanks for your help! Sridhar Purdue University -------------- next part -------------- An HTML attachment was scrubbed... URL: http://pwscf.org/pipermail/pw_forum/attachments/20140527/c11e8119/attachment.html -------------- next part -------------- A non-text attachment was scrubbed... Name: si.fc Type: application/octet-stream Size: 77476 bytes Desc: not available Url : http://pwscf.org/pipermail/pw_forum/attachments/20140527/c11e8119/attachment.obj