I think his intention is a molecular/metal cluster, not computer cluster.

 Thank you Vasantha Gowda.

My objective is how I can create an input file in gaussView (Na + Hen (n = 2-10) for example)

The best starting point for any QM calculations is the experimental structure (xray, nmr or any other experimental technique) of that system or anything similar. There are repositories of organic xray structures (CCDC), inorganic ones (ICSD) and/or you can always try to find these in published papers. 

For any new systems you can try with something that is chemicallt/physically feasible. Is the He in your example just a Helium atom? 

Dear Noureddine,

As Bartosz Trzaskowski noticed, it would be helpful if you have x-ray structure. In this case you may use Periodic Boundary Conditions tool in GaussView to create cluster of given size.

Is there any software where we can build new systems (crystal/clusters)?

Hi, All

I have optimized monomer of H2O2, now I want to make dimer, trimer and tetramer and so on. How can I make in Gauuview.

Any other software for the same. I tried Avagadro but when I am saving file it is not showing exact number of hydrogen and oxigen atomic positions for example if I am making dimer (taking two monomer) then it should 4 hydrogen and 4 oxigen cartesian positions but it is showing more than 8 positions same for  pentamer it is showing total more than 20 position but it should be 20 positions.

I would say ArgusLab. Draw and copy a single H2O2 molecule and paste as many as molecules you want. You can adjust the molecules also.

Thanks Saisudhakar, I will try to use ArgusLab.

Shilendra

Go to Edit-->PBC-->select the Cell/space group and add the atomic composition.

Nice to share the outstanding guides about "How to use GaussView" as follows:

1) https://www.mtholyoke.edu/courses/jwijngaa/PS/Gaussview2.pdf

2) https://www.tau.ac.il/~ephraim/intro2gaussview.pdf

3) https://gaussian.com/gv6main/

Have a good day@@@