Try using Quantum Espresso or some similar packages like, cp2k or wein2k.

I have used quantum espresso, if you have any queries regarding the same feel free to ask.

Try using Quantum Espresso or some similar packages like, cp2k or wein2k.

I have used quantum espresso, if you have any queries regarding the same feel free to ask.

If you talk about a large number of atom in nano field, you can use the " Siesta program". Regards

Hi Keshav,

In Gaussian16 there are many DFT functionals which can be utilized for nanoclusters. However, depending on what type of clusters (Metallic, nonmetallic, bimetallic etc) and what properties you want to study, some functional will perform better than the others. I'll highly recommend that you first read some literature which matches closely to your project (Properties and type of Clusters) and check what DFT functional they have used. This will give you an idea what type of functional is suitable for your work.

In short, you choice of functional will vary based on your cluster and your intended study and hence there is no straight answer to your question. However, based on my personal experience on clusters, older functional like B3LYP, PBE1PBE, TPSSh, M062X, BHandHLYP etc works quite well for a wide range of clusters. Now a days dispersion correction has become almost mandatory so you may need to include dispersion correction with these calculations (e.g: DFT-D3). In gaussian16 there are some new functional (like MN15 series). You can try them also. If your cluster is quite new and not widely studied you may require to benchmark first which functional gives better results and the proceed forward. One functional may not be suitable for all the properties you want to calculate. For example one functional may be really good for prediction of structure but may overestimate/underestimate the HOMO-LUMO gap. In this scenario you may require to use multiple different functional for different properties.

Also, another thing to remember, apart from the functional, you also need to choose good basis set for your system depending on what type of atoms you have within your cluster and the charged state of the cluster (cation or anion etc). The combination of functional and basis set will determine how accurate your results are.

All the best.

Thank you Anwesh Pandey M. A. Al-Kaabi for your answers.

Thank you Turbasu Sengupta for your answer. I want to study silver nanocluster. Most of the papers I have read either use codes like quantum espresso or PBE functional. That's why I ask this question. I will try benchmarking my chemical models against previous literature. I am not sure about basis set right now as I am intended to study large clusters ~30 Ag atoms. I will try triple 6-311++(2d,p) or its variation, LanL2DZ.

Thanks again for your informative answer.

If G16 is what you have to work with, it seems to me that you cannot go wrong with the MN15 functional (recommended by Turbasu Sengupta). Let me attach a PDF from the Truhlar group that also includes discussions on the performance of other functionals, many of which are available in G16. The big difference between G16 and "solid state" codes like VASP, Quantum Espresso, etc., is that G16 uses atomic orbital basis sets where as the latter group uses plane waves with periodic boundary conditions. Which one you use depends on what you plan to investigate. Good luck.

Thank you B. R. Ramachandran for your valuable suggestion. From your answer, I got a new question. The metallic nano clusters are not crystals. They are clusters without periodicity.

(My clusters have nearly similar structures as in one of your paper

Article Structure and Properties of Fen, Fen–, and Fen+ Clusters, n = 7–20

Is it appropriate to use codes with periodic boundary conditions? To me, atomic orbitals basis set seems correct because electronic cloud of an individual atom is localized and atomic orbitals basis set are also localized. But plane waves (in periodic boundary conditions) are not localized to a single atom. Is this correct or not?

A lot depends on the size of clusters and the properties you wish to study. As you can see, we look at small clusters and we are interested in structure, spin state, cluster dissociation energies, polarizability, etc., and we work mostly with the first row transition metals. We find that you really need to use all-electron basis sets for this, and they are available in Gaussian. If you want to study heavier elements, the use of pseudopotentials to screen out core electrons becomes necessary. If you want to study larger clusters (~30 atoms or more), it seems to me that a plane-wave DFT code (like VASP or Quantum Espresso) is needed. In that case you would put your cluster in the middle of a large box, and use a 1x1x1 k-point mesh (i.e., Gamma point sampling) with an appropriate energy cut-off. Caution: hybrid and meta-GGA functionals are computationally VERY demanding in these applications. If you are using VASP, PBE and RPBE (the version of Hammer, Hansen, and Norskov, 1999) are available and are usually reliable. RPBE may be slightly better for adsorption energy calculations (as in catalysis).

Thank you B. R. Ramachandran sir for your informative answer. I learn a lot form it.