[cclib-users] A question about LPA

[Martin R. <mar...@gm...>]

Dear List,

I'm running a trial Löwdin population analysis (LPA) on SF6, from a
 B3LYP/cc-pVTZ calculation. Something is awry, the total number of
electrons gets overestimated by 0.3 (70.3), and there is a "complex
warning" when running the LPA.

LPA is supposed to be rotationally invariant if one use "pure" spherical
harmonics in the basis set, e.g. 5 d functions instead of 6. (which cc-pVTZ
does). Anyone have any clue to this behavior?

Best regards,
Martin

Gaussian Input: ---------
# opt freq b3lyp/cc-pvtz pop=(nboread,full) iop(3/33=1,3/36=-1)

Title Card Required

0 1
 F                  0.00000000    0.00000000    1.57972200
 F                  0.00000000    1.57972200    0.00000000
 F                  0.00000000    0.00000000   -1.57972200
 F                  0.00000000   -1.57972200    0.00000000
 F                  1.57972200    0.00000000    0.00000000
 F                 -1.57972200    0.00000000    0.00000000
 S                  0.00000000    0.00000000    0.00000000

Python script: --------
from numpy import *
from cclib.parser import ccopen
from cclib.method import LPA
parser = ccopen("test.log")
data = parser.parse()
method = LPA(data)
method.calculate()
savetxt("LPA-big.csv",transpose(2*method.aoresults[0][:data.homos[0]+1]))

Script output: --------
...
[Gaussian test.log INFO] Creating attribute coreelectrons[]
[LPA <cclib.parser.data.ccData object at 0x1015ba150> INFO] Creating
attribute aoresults: [array[2]]
/Library/Frameworks/Python.framework/Versions/2.7/lib/python2.7/site-packages/cclib/method/lpa.py:99:
ComplexWarning: Casting complex values to real discards the imaginary part
  self.aoresults[spin][i] = numpy.multiply(temp1, temp2).astype("d")
[LPA <cclib.parser.data.ccData object at 0x1015ba150> INFO] Saving
partitioned results in fragresults: [array[2]]
[LPA <cclib.parser.data.ccData object at 0x1015ba150> INFO] Creating
fragcharges: array[1]