Dear Mostafa Torkashvand,

I suggest you see the links on the topic.

https://www.scm.com/doc/Tutorials/ExternalPrograms/VASPTiO2SurfaceRelaxation.html

https://www.semanticscholar.org/paper/A-Study-of-Potential-Organometallic-for-TiO2-Using-Colman-Melendez/6866717fa6e4c2648630d8bb035b214335031450

https://ww.vasp.at/forum/viewtopic.php?p=7321

https://www.tipure.cn/-/media/files/tipure/legacy/titanium-dioxide-for-coatings.pdf?rev=70975dd1245f4082841a13ef41058282

https://mattermodeling.stackexchange.com/questions/8574/the-comparison-of-bandgap-value-of-slab-and-bulk-phase

http://uu.diva-portal.org/smash/get/diva2:1510518/FULLTEXT01.pdf

Best regards

Dear Mostafa Torkashvand ,

You may find the following resource useful for the case at present.

https://www.molphys.org/VASP/volume.html