I have Pyrope (Mg3Al2(SiO4)3) crystal structure, downloaded from materialsproject: 
<https://materialsproject.org/materials/mp-6073/#>

It appeared as triclinic cell, but if you download CIF file and open it from softwares like Avogadro or VESTA, it appeared as a orthogonal simple cubic (a=b=c, alpha = beta = gamma = 90 degree). I also checked that this geometry is the same with what I downloaded from American Mineralogy Material Database. 

Now, I wish to run DFT or quantum calculations for them. So, I excluded atoms in periodic boundary, unit cell contains total 160 atoms. I'm afraid this might be too big, might takes too long time to calculate via DFT or any other quantum simulations. All I need to do is just geometry optimizations, but still, 160 atoms seems too big. 

Using VESTA or Avogadro or any other software, is this possible to find the symmetric structure inside this or other "big" unit cell, and make a smaller / simpler version of unit cell for faster calculation? 

Or, can I manually cut this unit cell in 1/4 size, 40 atom system with 1/2 size for x, y, and z direction, and run the minimization? It seems that the Pyrope unit cell have some sort of repeating structure inside the big unit cell. But I'm not sure if it is "safe" to find symmetry and divide the unit cell manually. 

Thank you