QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: Dmitry on July 12, 2012, 13:41

Title: Maximum number of atoms
Post by: Dmitry on July 12, 2012, 13:41

What is the maximum number of atoms in molecule wich it is possible to calculate by DFT/LDA/PW?

Title: Re: Maximum number of atoms
Post by: Anders Blom on July 12, 2012, 13:51

Infinitely many. Well, if you have a computer with infinite amount of memory, and you are prepared to wait infinitely long :)

If not, then it is still not really a simple question to answer. It depends on - again - how much memory your computer has, how long you are willing to wait, but also what kind of system you are looking at. For ATK, which uses numerical orbitals, what matters is not the number of atoms but the number of orbitals, and larger atoms like Au require more orbitals than C, say, so with a given amount of resources you can simulate fewer Au atoms than C.

But a rough number is 1,000 atoms. Above that it gets very heavy, but even below that it can be hard for e.g. heavy elements in a dense configuration.

Title: Re: Maximum number of atoms
Post by: Dmitry on July 13, 2012, 10:29

I see. Thank you.

Title: Re: Maximum number of atoms
Post by: coollailai on July 13, 2012, 11:25

In my group, we usually use the model containing under 400 atoms. However, we only have several servers.