Hot answers tagged

20

ORCA The local pair-natural orbital (DLPNO) based coupled cluster method have been managed to investigate large organic molecule and small proteins (linear C150H302 (452 atoms, >8800 basis functions) , Crambin with 644 atoms, and more than 6400 basis functions ,C350H902 (>1000 atoms, > 20000 basis functions)). Riplinger, C., Sandhoefer, B., Hansen, ...


10

I’ll expand on this later but here is the abbreviated version. CTF The CTF code can do very large iterative CCSD and CCSDT using a dense spin-orbital formalism. CCSD up to 55 (50) water molecules with cc-pVDZ http://solomonik.cs.illinois.edu/talks/molssi-monterey-may-2017.pdf The 8-water CCSDT problem in Table 3 took 15 minutes on 1024 nodes of BG/Q and ...


8

Major Issue The major issue here is that NWChem doesn't support second-order response in the DFT code: "Response calculations are currently supported only for order 1 (linear response), single frequency, electric field and mixed electric-magnetic field perturbations." [1] The NWChem coupled-cluster response property capability supports ...


7

Localized natural orbitals methods allow tackling huge system sizes; some links were already given above. Of course, the accuracy remains sometimes a question in such methods: the methods rely on thresholds, which may not have always been converged! So you should keep in mind that these are not black-box tools like conventional coupled-cluster theory. The ...


7

In general, you should use the $S_1$ state by default, unless you have reasons to suspect that your molecule is anti-Kasha. IMHO satisfying one of the following criteria guarantees that your molecule obeys the Kasha rule (supposing that your calculation is accurate), and you basically need not suspect otherwise: The experimental fluorescence spectrum ...


5

You should consider the states (roots) with non-zero oscillator strength. It means that the transition from the ground to excited state is allowed by the transition dipole moment rule. So, in your case root number 3 is the first excited state with oscillator strength of 0.16, whilst root number 5 is the second excited state with oscillator strength of 0.24. ...


4

It turns out, that NWchem do not support K-points with Gaussian basis. The nwpw section in my input files, that contains the K-point grid specification, actually configures another calculation (with plane-wave basis) that is never launched by the task directive. Summing up, with NWchem you can use either K-points with plane-waves, or a supercell with ...


Only top voted, non community-wiki answers of a minimum length are eligible