Notes on Quantum Chemistry Software

#Notes on Quantum Chemistry Software

Comparison of Pople's and TURBOMOLE basis sets

NOTE: the following discussion addresses only def2 sets [1], cause why bother using old stuff?! [2].

• Adding a set of p-type polarization functions to SV(P) basis for hydrogen atoms results in SVP basis set (should be similar to 6-31G**).
• Diffuse functions (+ and ++ [for H atoms] in Pople's language) are fresh out the print for def2 sets [5]: def2-SVPD, etc.

the B3LYP story

A discussion on how the patient is constructed is here [3].

Energy Comparison: Gaussian vs Turbomole

Some people actually are trying to do this ;) [4].

Molecular Orbitals (Wavefunctions) from TM in Cube Format

Need to start from the fully converged energy.

$pointval mo 195-204 fmt=cub

Setting up calculation for an anion (spin multiplicity -- doublet, if ground state was singlet)

1. Run eiger in converged scf directory, the result should be (note 422 electrons):

   Number of MOs= 1632, Electrons= 422.00, Symmetry: ci Nr. Orbital Occupation Energy [...] 214. 107 au -0.057162 H = -1.555 eV 213. 107 ag -0.066817 H = -1.818 eV 212. 106 au -0.103638 H = -2.820 eV 211. 106 ag 2.000 -0.181013 H = -4.926 eV 210. 105 au 2.000 -0.217198 H = -5.910 eV 209. 105 ag 2.000 -0.228733 H = -6.224 eV [...]

2. Run define in the desired dir, eth should make 106-au orbital half occupied (note 423 electrons).

   [...] ENTER THE MOLECULAR CHARGE (DEFAULT=0) -1 NUMBER OF ELECTRONS IN YOUR MOLECULE IS 423 [...] ORBITAL SYMMETRY ENERGY ALPHA OCC. BETA OCC. (SHELL) TYPE PER ORBITAL PER ORBITAL [...] 210 105ag -0.36903 1 1 211 106ag -0.36373 1 1 212 106au -0.34863 1 0 213 107ag -0.31022 0 0

VASP

ISMEAR (automatic generation of kpoints' mesh)

The method of MP is also the method of choice for large supercells, since the tetrahedron method is not applicable, if less than three k-points are used.

-- whooray!

Ionic Relaxations

1. Add NELMIN=10 in the electronic relaxation block (aka SCF), suggested for MD ()
2. Projections should be done in the reciprocal space: LREAL = .FALSE.. (expand here)
3. Add dispersion correction: LVDW = .TRUE. in the ionic relaxation block. Remember, dispersion correction is just an energetic term that is added to the (SCF) converged energy value. It is not important for eletronic relaxations (since it is just a shift), but it is important for ionic ones.

Gaussian

Change omega (long-range correlation parameter) in omega-functionals in Gaussian (older than 09 Rev B.01)

Input.gjf:

#P wB97 IOp(3/107=0262000000) IOp(3/108=0262000000)

Title: Omega = 0.262 Bohr^(-1)

0 1
C 0.000 0.000 0.0000

Output.log, note HFx wLong and DFx wLong:

[...]

IExCor= 4437 DFT=T Ex+Corr=wB97 ExCW=0 ScaHFX=  1.000000
 ScaDFX=  1.000000  1.000000  1.000000  1.000000 ScalE2=  1.000000  1.000000
 IRadAn=      0 IRanWt=     -1 IRanGd=            0 ICorTp=0
  HFx wShort=  0.000000 wLong=  0.262000 cFull=  0.000000 cShort=  0.000000 cLong=  1.000000
  DFx wShort=  0.000000 wLong=  0.262000 cFull=  0.000000 cShort=  0.000000 cLong=  1.000000

[...]

#References

1. dx.doi.org/10.1039/B508541A
2. http://goo.gl/D2I7l
3. http://goo.gl/tti01 and http://goo.gl/mLhKc
4. http://www.turbo-forum.com/index.php?topic=192.msg520#msg520