Dear Sir Amitava Ghosh for double or triple-phase refinement of a sample in Fullprof software, you have to use different cif.

If you want multiphase refinement of a sample, first refine with the major phase that is matched with the sample. After fitting all the necessary parameters, add the other phases that you want to refine.

This is the process of multiphase refinements. You cannot use a single cif for your double-phase refinement.

Thank You.

Dear Amitava Ghosh,

You can try to create an XRD card in Fullprof on your own. See the materialsproject site (https://next-gen.materialsproject.org/materials) and try to find your double perovskite with the same crystallographic space group. Then you can just add atoms and atomic positions according to the information that you just found in the materialproject. There are many training videos on how to do Rietveld refinement in Fullprof on YouTube, so you can find exact steps on how to add an XRD card for refinement.

Hi, I suggest to do basic good old fashioned research following the literature to find a related phase prior to asking people to do the work for you.

Just by typing " double perovskite space group Pna21" any search machine will likely pop up a reference to the publication

Phase Transitions of AlFeO3 and GaFeO3 from the Chiral Orthorhombic

(Pna21) Structure to the Rhombohedral (R3c) Structure

Rana Saha, Ajmala Shireen, Sharmila N. Shirodkar, Mukta Shashi Singh, Umesh V. Waghmare,

A. Sundaresan, and C. N. R. Rao* in "Inorganic Chemistry" norg. Chem. 2011, 50, 9527–9532.

By actually reading this paper you will quickly get to reference number 4:

4) Bouree, F.; Baudour, J. L.; Elbadraoui, E.; Musso, J.; Laurent, C.;

Rousset, A. Acta Crystallogr. 1996, B52, 217.

Searching for this reference you will find straightforwardly the original publication or here (!) on Researchgate the site:

Article Crystal and Magnetic Structure of Piezoelectric, Ferrimagnet...

which includes a link to a CIF file that contains two double perovskites in space group Pna21.

As your original question lacks details on the actual perovskite chemistry etc, the actual cif file must be taken cautiously as a template.

Dear all, I have solved the problem using data (lattice parmeters, atomic positions for Pna21 space group) from a perovskite paper. Thank you all for your answers.