ADC(2)/COSMO oscillating macro-iteration

[martijn]

Hi,

I'm trying to calculate the vertical absorption spectrum of a solvated molecule using ADC(2)/cosmo in Turbomole 7.01 using the following set-up:

$ricc2
  adc(2)
  maxiter=  300
$excitations
  irrep=a  multiplicity=  1  nexc=  6  npre=  12  nstart=  12
  exprop relaxed states=all
$response
  fop relaxed
$cosmo
  epsilon=   80.10
  refind=   1.3000
  cosmorel state=(x)
# nofast

The calculation seems to work well and give reasonable "intermediate" results but the problem is that the CC2 macro-iteration doesn't converge but keep oscillating between two solutions:

# all values without outlying charge correction
# (outlying charge corrected values can be found in the output file)
#
# cycle    E(total)           E(diel MP2)           E(MP2)      delta charge (rms) delta charge(max)
  0    -230.9179247982      -0.0918744074      -0.7887838009  0.11728E-03 -0.38742E-03
  1    -230.9179279656      -0.0918274695      -0.7888597778  0.15186E-04  0.57729E-04
  2    -230.9179952351      -0.0919500778      -0.7888186002  0.14160E-03 -0.61505E-03
  3    -231.0083829481      -0.0897466651      -0.6916637848  0.95790E-03 -0.51521E-02
  4    -231.0085872186      -0.0900389684      -0.6904770570  0.96849E-03 -0.41291E-02
  5    -231.0075591068      -0.0897390899      -0.6898607103  0.86563E-03 -0.32236E-02
  6    -231.0090768302      -0.0904210576      -0.6908517897  0.99019E-03 -0.35151E-02
  7    -231.0071105859      -0.0895805032      -0.6894392888  0.89380E-03  0.31910E-02
  8    -231.0096324466      -0.0907804235      -0.6912538795  0.10140E-02  0.36228E-02
  9    -231.0067686452      -0.0894757752      -0.6890876373  0.93968E-03 -0.33503E-02
10    -231.0096890783      -0.0909058888      -0.6914381872  0.98338E-03  0.35246E-02
11    -231.0066560484      -0.0894432884      -0.6889677043  0.95845E-03 -0.34345E-02
12    -231.0094676545      -0.0904698272      -0.6916996326  0.87135E-03  0.32291E-02
13    -231.0068609427      -0.0894847999      -0.6891893971  0.91599E-03 -0.33874E-02
14    -231.0098293233      -0.0908624643      -0.6915076141  0.99917E-03  0.36195E-02
15    -231.0066566914      -0.0894421317      -0.6889729765  0.95574E-03 -0.34609E-02

What could be the cause of this oscillation and how can I force it to converge.

Thanks,

Martijn

[christof.haettig]

If the gap between the ground and the lowest excited state is so small that they interchange from vacuum to solution this can cause problems for the PTED-COSMO calculations.
Check if the occupation of the orbitals after the COSMO-SCF is correct.