You can either input the experimental determined structure using the cif file or build the structure yourself.

If you build yourself, in a new 3D Atomistic window input the space group, then lattice constants, you will see a new lattice on the window. This time, add atoms by clicking add atoms. The the experimetal determined structure is on the window as the input.

For geometry optimization, I suggest you to use the experimental determined structure as a input and then compare the geometry optimized with the experimetal one. The reliability depends on how small the difference is.

Does Materials Studio allow you to input .cif files?  If so, here is the one for lithium carbonate.  That should  reassure you about how it is entered.  https://github.com/cryos/avogadro/blob/master/crystals/carbonates/Li2CO3-Zabuyelite.cif

As Prof. Merola suggested, the simplest way is to import the structure (in such a case you are a lucky guy). If you have defined the unit cell (lattice parameters and fractional coordinates of the atoms) then you have to manually define the unit cell:  space group symmetry (Meniu: Build/Crystals/Build crystals ...) and define the atom positions (Meniu: Build/Add Atoms...). If you have no info about the system structure then you are on your own, as you have to establish yourself the most stable polymorph by a complex work. You might guess some initial structures and build it or try highthroughput screening using as initial structures the known systems with similar chemical formula, but with different atom types. [see J.C. Cole, Acta Cryst. B72 (2016) 530] Then you optimize each structure and see which one has the lowest energy (to be correct, you have to build the G(P,T) phase diagram, where G-Gibbs Energy, P - Pressure and T - Temperature).

Luckily there are some.methods (genetic algorithm, particle swarm, annealing-quenching, basin hoping, stochastic search, ...) and tools (CALYPSO, Gasp, Grace, USPEX, XTalOpt) that might help you to predict the crystal structure. See the discussion in M. O’Keeffe Phys. Chem. Chem. Phys., 12 (2010) 8580 and in other articles in the same special issue of PCCP.  

You can either input the experimental determined structure using the cif file or build the structure yourself.

If you build yourself, in a new 3D Atomistic window input the space group, then lattice constants, you will see a new lattice on the window. This time, add atoms by clicking add atoms. The the experimetal determined structure is on the window as the input.

For geometry optimization, I suggest you to use the experimental determined structure as a input and then compare the geometry optimized with the experimetal one. The reliability depends on how small the difference is.

Thank you very much Prof. Joseph S Merola. Yes my MS support the cif file and as you suggested I have tried the with the cif file. It works.Thank you again.

And also thank you Dr. Viorel Chihaia  and Prof. Yanchun Zhou for the reference.

Dear Arindam,

                                   I'm not familiar with the use of MS program, and prefere working starting from CIF file. Nevertheless,  my research group reached a good level of knowledge about Li2CO3 (mineral zabuyelite) working on single crystal and twin growth ', both experimentally and theoretically. I would like to send you some papers in which structure and morphology of Li2CO3 are strictly related.

Another interesting paper about Li2CO3 has been published by Bruno, M.; Prencipe, M. Surface Science 601 (2007) 3012-3019

Thanks for your interest !

Dino

Thank you very much Professor Dino Aquilano for the resources. I would like to have them.

Can any one step by step working of organic inhibitor on iron (mild steel) in HCl medium in materials studio  software 7.