[molpro-user] CCSD natural orbitals

[Alan Chien]

I'm toying with CCSD natural orbitals for butadiene as a starting point for
higher level calculations. Full input included at the end.

{ccsd;
expec,type=norelax;
dm,2141.2;
natorb,record=2141.2,print=23,*core*=0;
}

I'm confused as to the function of "*core*". The manual (
https://www.molpro.net/info/2015.1/doc/manual/node341.html#sec:natorb_mp2)
states that core=1 freezes the core orbitals when constructing the density
matrix.

If I'm already using the frozen-core approximation in my CCSD calculation,
which I am, why does setting core=1 change my NO occupancy results? The
core orbitals should not be coupled to the rest of the orbitals at all in a
non-relaxed density matrix, so it should not matter if the core orbitals
are included or not in the density matrix.

Any insight appreciated,
Alan Chien



*Input below*

***,buta
geometry={
  C         0.6009903066   -0.4020172170    0.0000000000
  C        -0.6009903066    0.4020172170    0.0000000000
  C         1.8329498097    0.1103686968    0.0000000000
  C        -1.8329498097   -0.1103686968    0.0000000000
  H         1.9876059086    1.1777308428    0.0000000000
  H        -1.9876059086   -1.1777308428    0.0000000000
  H         0.4702284110   -1.4752930006    0.0000000000
  H        -0.4702284110    1.4752930006    0.0000000000
  H         2.7040838288   -0.5215644347    0.0000000000
  H        -2.7040838288    0.5215644347    0.0000000000
}
basis=roos(3s2p1d/2s1p) !anos-l-pvdz
{hf;
orbprint,5;
}
{ccsd;
expec,type=norelax;
dm,2141.2;
natorb,record=2141.2,print=23,core=0;
}
{put,molden,ccsd.molden;
orbital,record=2141.2,type=natural
}
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://www.molpro.net/pipermail/molpro-user/attachments/20170314/fcaee6a8/attachment.html>