Hi, fcbuild just sets up the crystallography for latter use by vibra. What are the correct parameters for running siesta, such as to get the force constants matrix, is still your responsibily. Thus, a) add the slabdipolecorrection and the k-point grid you already used.
b) not sure you can do that easily; you might try to perform the siesta run with constraints, namely, fix every coordinate but those of the acid. This will produce a reduced force constants matrix (*.FC file) to feed vibra ... and hopefuly ... Regards, Roberto On 08/22/2014 06:47 AM, Geldof Davy wrote:
Dear Siesta users, I am calculating vibrational frequencies with the vibrator package. The system consists of a titanium oxide surface adsorbing an acid. I first did geometry optimization with slabdipolecorrection and a certain k-grid. Then I want to calculate the vibrational frequencies of the acid: a) When applying the fcbuilld, I noticed that both slabdipolecorrection and k-grid is not taken into account. Is it necessary to add both parameters to calculate the vibrational frequencies or is a calculation considering only the gamma point sufficient? b) I am mostly interested in the vibrational frequencies of the acid on the surface. Is it possible to calculate only the vibrational frequencies of the acid? Kind regards, Davy Geldof Structural Chemistry Group, Department of Chemistry University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium [email protected]
