I am a student and need high processing computers(cluster) for quantum calculations. Would you please introduce me any website which i can use their computers freely?
I also have this same problem. I think XSEDE is only for U.S. based institutes. The super computer doesn't look really free it requiring me for payment system when I start the trial account.
HPCs are definitely required for calculations related to quantum chemistry but I don't think there would be any place to offer their clusters for free or if there is you're gonna have to wait a long time in the que. As your university is in Iran you can access these clusters with pretty good prices. I recommend www.astek.ir in which you can access as many cores as you wish or GPU with reasonable price and also with good offers. And I think you may not need more than 20 processors but depending on your molecule geometry and atom type (especially using Gaussian and Quantum Espresso) you will need hard disk. They also have the softwares you mentioned installed.