Population

CHARGE SAVE OPTIONS

SaveType
Computed atomic charges can be stored on the checkpoint file for use in a later MM calculation withGeom=Check. The optionsPop=SaveMulliken,Pop=SaveESP,Pop=SaveNPA,Pop=SaveCM5, and so on can be used to save the corresponding charges. In the case of a multilayer ONIOM calculation, only explicitly computed charges are saved by default: i.e., charges for atoms in the QM layer(s). Any atomic charges present in the input file will not be used and they will be replaced by the newly fitted charges saved by these options.

The additional optionUnchargedwill keep the atomic charges present in the input file and only fit charges on uncharged
atoms in the QM layers(s). The option combinationsPop=(Uncharged, SaveMulliken),Pop=(Uncharged, SaveCM5)and so on will save both the original atomic charges plus the newly fitted charges for the atoms that were originally uncharged.

NATURAL ORBITAL-RELATED OPTIONS

NaturalOrbitals
Do a natural orbital analysis of the total density.NOis a synonym forNaturalOrbitals.

NOAB
Do separate natural orbital analyses for the α and β densities.NaturalSpinOrbitalsis a synonym forNOAB.

AlphaNatural
Do separate natural orbital analyses for the α and β densities, but store only the α densities for use in a.wfnfile (seeOutput=WFN).NOAis a synonym forAlphaNatural.

BetaNatural
Do separate natural orbital analyses for the α and β densities, but store only the β densities for use in a.wfnfile (seeOutput=WFN).NOBis a synonym forBetaNatural.

SpinNatural
Generate natural orbitals for the spin density (with α considered positive).

By default, natural orbitals are not included in the checkpoint file. Use a second job step of this form to place the natural orbitals into the checkpoint file:

--Link1-- %Chk=name# Guess=(Save,Only,NaturalOrbitals) Geom=AllCheck ChkBasis

Run theformchkutility on the resulting checkpoint file to prepare the orbitals for visualization.

OPTIONS FOR GENERATING ELECTROSTATIC POTENTIAL-DERIVED CHARGES

MK
Produce charges fit to the electrostatic potential at points selected according to the Merz-Singh-Kollman scheme[Singh84,Besler90].ESPandMerzKollmanare synonyms forMK. The data file for Antechamber (the AMBER program for generating RESP charges) can be generated usingPop=MK IOp(6/50=1).

MKUFF
MK fitting, but using UFF radii, defined for all elements.

CHelp
Produce charges fit to the electrostatic potential at points selected according to the CHelp scheme[Chirlian87].

CHelpG
Produce charges fit to the electrostatic potential at points selected according to the CHelpG scheme[Breneman90].

HLY
Hu, Lu, and Yang charge fitting method[Hu07].

HLYGAt
Hu, Lu, and Yang charge fitting method, but using Gaussian's standard atomic densities instead of those of HLY. The authors ofHLYonly parametrized the atomic densities required for the model for the first 18 elements. This is an alternative version that uses the HLY fitting scheme but with Gaussian’s standard atomic densities, which are available for the entire periodic table. For systems which can be done either way, the difference in atomic charges is usually between 1% and 5%.

Dipole
When fitting charges to the potential, constrain them to reproduce the dipole moment.ESPDipoleis a synonym forDipole.

AtomDipole
When fitting charges to the potential, also fit a point dipole at each atomic center.

ReadRadii
Read in alternative radii (in Angstroms) for each element for use in fitting potentials. These are read as pairs of atomic symbol and radius, terminated by a blank line.

ReadAtRadii
Read in alternative radii (in Angstroms) for each atom for use in fitting potentials. These are read as pairs of atom number and radius, terminated by a blank line.

NBO-RELATED OPTIONS (VERSION 3)

NBO
Requests a full Natural Bond Orbital analysis, using NBO version 3[Foster80,Reed83a,Reed85,Reed85a,Carpenter87,Carpenter88,Reed88,Weinhold88].

NCS
Requests a partitioning of the NMR shielding tensors (computed using GIAOs) into magnetic contributions from bonds and lone pairs using the Natural Chemical Shielding analysis of Bohmann et al.[Bohmann97], which is based upon the NBO analysis method. By default, an analysis of the isotropic shielding is performed.NoNCSskips this analysis.

NCSDiag
Requests an NCS analysis of the diagonal tensor elements.

NCSAll
Requests an NCS analysis of all tensor components.

NPA
Requests just the Natural Population Analysis phase of NBO.

NBORead
Requests a full NBO analysis, with input controlling the analysis read from the input stream. Use this option to specify keywords for NBO. Refer to the NBO documentation for details on this input.

NBODel
Requests NBO analysis of the effects of deletion of some interactions. Only possible with SCF methods. Implies that NBO input will be read; refer to the NBO documentation for details. Note that NBO input starts in column 2 so that the UNIX shell does not interpret the initial$.

SaveNBOs
Save natural bond orbitals in the checkpoint file (for later visualization).

SaveNLMOs
Save natural localized molecular orbitals in the checkpoint file (for later visualization).

SaveMixed
Save the NBOs for the occupied orbitals and the NLMOs for the unoccupied orbitals in the checkpoint file (for later visualization).

NBO-RELATED OPTIONS (VERSION 6)

An interface to NBO version 6 is provided.Pop=NPA6,Pop=NBO6,Pop=NBO6ReadandPop=NBO6Deleterequest use of the separate NBO6 program via the external interface. The script required to run NBO6 and the program itself must be obtained from Frank Weinhold (nbo6.chem.wisc.edu).

RELATED KEYWORDS

Density, Output=WFN

EXAMPLES

Orbital-by-Orbital Population Analysis.The following route section requests population analysis of the lowest 3 virtual orbitals and the highest 3 occupied orbitals:

# UHF/6-311+G(d) Pop=Orbitals=3

Here is the resulting output from a calculation on FeO+ quartet:

Atomic contributions to Alpha molecular orbitals: Alpha occ 16 OE=-0.923 is Fe1-d=1.00 Alpha occ 17 OE=-0.699 is O2-p=0.88 Alpha occ 18 OE=-0.690 is O2-p=0.68 Fe1-s=0.21 Alpha vir 19 OE=-0.253 is Fe1-s=0.70 Fe1-p=0.27 Alpha vir 20 OE=-0.188 is Fe1-p=0.71 O2-p=0.29 Alpha vir 21 OE=-0.133 is Fe1-p=1.04 Atomic contributions to Beta molecular orbitals: Beta occ 13 OE=-0.801 is O2-p=0.79 Beta occ 14 OE=-0.783 is Fe1-d=1.00 Beta occ 15 OE=-0.758 is O2-p=0.89 Beta vir 16 OE=-0.241 is Fe1-s=0.81 Fe1-p=0.17 Beta vir 17 OE=-0.139 is Fe1-p=0.91 Fe1-d=0.14

Note that both alpha and beta orbital information is included. For each orbital, the output reports the orbital energy (labeled OE and given in atomic units), followed by the fractional contribution of all basis functions of a given angular momentum for each relevant atom.

This is an example of a system where it is hard to tell the spin state of the system, because the canonical α and β orbitals are quite different. If you subsequently run aGuess=(Read,Only,BiOrthogonalize) Pop=Orbitalcalculation to analyze the results, then the program transforms the α and β orbitals to match up as much as possible (occupied and virtual separately). In this case, orbital energies for the transformed orbitals are nor given. Rather, thePop=Orbitalanalysis reports the overlaps between the pairs of corresponding orbitals (i.e., α 19 with β 19), with a value of 1 indicating 100% correspondence. Instead of labeling the orbitals as occupied or virtual, they are labeled:

The program lists the orbitals which match another orbital only once within the output. Also, for each unpaired excess alpha spin occupied orbital, there is always some beta virtual orbital which matches it, and the latter are also omitted.

Here is the output for FeO+ quartet, which has 3 more alpha electrons than beta but which turns out to really have 4 unpaired alpha occupieds and one unpaired beta occupied (the lowest doubly occupied and highest unoccupied orbitals have been cut from the output):

Atomic contributions to molecular orbitals: Docc. orb 13 abOv=0.999 is Fe1-d=1.00 Docc. orb 14 abOv=0.990 is O2-p=0.72 Fe1-s=0.14 Fe1-d=0.14 Asing orb 15 abOv=0.316 is Fe1-d=0.99 Asing orb 16 abOv=1.000 is Fe1-d=0.94 Asing orb 17 abOv=1.000 is Fe1-d=0.91 Asing orb 18 abOv=1.000 is Fe1-d=0.91 Dvirt orb 19 abOv=1.000 is O2-s=1.92 Fe1-s=-0.67 O2-p=-0.43 Fe1-p=0.14 Dvirt orb 20 abOv=1.000 is Fe1-s=0.52 Fe1-p=0.37 Bsing orb 15 abOv=0.316 is O2-p=0.92

Orbitals 1-14 are doubly occupied. Alpha orbital 15 and beta orbital 15 are different singly occupied orbitals; all 4 unpaired alpha spins are on the Fe, and the one unpaired beta spin is on the oxygen. There are no unmatched alpha and beta virtuals within the default range of orbitals analyzed.

Fragment Level Decomposition.If fragment information is present, the output also reports populations over fragments. ForPop=Orbitaljobs, the decomposition of each orbital by fragment is reported.

Default output including fragment populations:Mulliken charges with hydrogens summed into heavy atoms: 1 1 Pd -0.265855 2 P 0.346314 3 P 0.346314 4 Cl -0.168156 5 Cl -0.168156 6 C 0.060982 7 C 0.060982 8 C -0.106213 9 C -0.106213 Sum of Mulliken charges with hydrogens summed into heavy atoms = 0.00000 Condensed to fragments (all electrons): 1 -0.265855 2 -0.168156 3 -0.168156 4 0.060982 5 0.060982 6 0.480203Pop=Orbital output:Alpha occ 60 OE=-0.247 is Cl4-p=0.22 Cl5-p=0.22 P3-p=0.12 P2-p=0.12 Fr6=0.36 Fr2=0.22 Fr3=0.22

Sample NBO 3 Input.The following input file requests a bond order analysis using NBO 3:

# B3LYP/6-31G(d,p) Pop=NBORead Example of NBO bond orders 0 1 C 0.000000 0.665676 0.000000 H 0.919278 1.237739 0.000000 H -0.919239 1.237787 0.000000 C 0.000000 -0.665676 0.000000 H -0.919278 -1.237739 0.000000 H 0.919239 -1.237787 0.000000 $nbo bndidx $end

Last update: 16 April 2013