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1 vote

Cannot reproduce excitation energies in Orca

There are lots of reasons that calculated excited state energies won't match experimental values. Have a look at a good textbook on TD-DFT for why, but in general calculated energies will be higher in ...
leeman's user avatar
  • 171
4 votes
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Orthonormality of AOs and MOs in PySCF

Solving the Hartree-Fock equations is equivalent to unitary rotations of the orbitals, but you are missing the key piece: before Hartree-Fock, the basis set is orthonormalized to produce an ...
Susi Lehtola's user avatar
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6 votes
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Why use PySCF/OpenMolcas instead of VASP/QuantumESPRESSO

The main difference is that PySCF, OpenMolcas, and other popular software such as Gaussian, ORCA, Molpro, Psi4, MRCC, CFOUR, Dalton, GAMESS, COLUMBUS, ACES, etc., are very well-developed for using ...
Nike Dattani's user avatar
  • 34.7k
0 votes

Creating a Hypothetical Hexagonal Monolayer Structure Similar to MoS2

I strongly advise using online databases/projects to obtain the CIF/POSCAR files. One that I recommend is The Material Project: Here, you can search for materials information by chemistry, ...
Camps's user avatar
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5 votes

MOPAC: Is there a simple way to display geometry trajectories

I created a Python script to manipulate the MOPAC output, saving a XYZ file with all the structures from the optimization step. Then, the XYZ can be loaded into Jmol software and do the animation. The ...
Camps's user avatar
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4 votes
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Blind docking and targeted docking

If you already know where the active site of your protein is, there is no need to run a blind docking. Because the ligand binds to the protein, it doesn't imply that it can have any inhibitory action. ...
Camps's user avatar
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4 votes
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Making Deuterium POTCAR file for optimization in VASP software

Hydrogen and deuterium are basically identical electronically (*) and you should use the same pseudopotential (POTCAR) for each. You should not see any difference between hydrogen and deuterium (or ...
Phil Hasnip's user avatar
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3 votes

What is the best way to optimize molecules with 8000 atoms. This includes C,H,O,N,Si

First, "best" is ill-defined. The best method would be full configuration interaction at the complete basis set limit including fully relativistic and quantum field theoretical corrections; ...
Susi Lehtola's user avatar
  • 18.4k
1 vote
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Geometry of H2O in the v=1 vibrational state for AIMD simulation

"Geometry" is complicated in quantum mechanics, because we have probability distributions rather than precise geometrical positions as we would have in classical mechanics. If we make the ...
Nike Dattani's user avatar
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2 votes
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How to orthonormalize a set of Molecular orbitals?

Since S is created from orthonormal orbitals, it has 1.00 as diagonal elements. If ${\bf S}$ is created from orthonormal orbitals, the overlap matrix is simply the unit matrix, ${\bf S}={\bf 1}$. ...
Susi Lehtola's user avatar
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