# CP-MCSCF bug

Chris Evenhuis ceven at rsc.anu.edu.au
Tue Nov 4 01:25:31 GMT 2003

```I am calculating the the energy derivatives and NACMEs for H3 using
6-311G.  I am using two state averaging but have been looking at the
other states by using
state,3 weight,1,1,0
and
state,8 weight,1,1,0,0,0,0,0,0

For some geometries there is a large difference between the NACMEs and
the difference of the energy gradients.  However, the energies, the sum
of energy gradients and the CI vectors are equal.  The  discrepancy in
the NACME falls of inversely as the geometry is distorted away from the
bad point so it looks like a conical intersection (all energies are
well separated though).

the input files are

***,h3
geomtyp=xyz
gprint,orbitals,civector
geomtyp=xyz
geometry={nosym;noorient;
3
a comment
H1, 0.0000000000000000E+00, 0.0000000000000000E+00,
0.0000000000000000E+00
H2, 0.0000000000000000E+00, 0.1073111972324246E+01,
0.0000000000000000E+00
H3, 0.0000000000000000E+00,-0.8305234896369812E+00,
0.4101461803747558E+01
}
basis=6-311G
hf,3,1,0
multi
wf,3,1,1
!!!!!  Uncomment one or other !!!!
!     state,8
!     weight,1,1,0,0,0,0,0,0
!     state,3
!     weight,1,1,0
start,3003.2
accuracy,gradient=1.0e-8,step=1.0e-4,energy=1.0e-8
noextra
maxiter, 40;
iterations;dont,internal,1,5;end;
iterations;uncouple,5,to,10;end;
orbitals,3000.2

cpmcscf, grad,1.1,spin=0.5,accu=1.d-11,save=5101.1
cpmcscf, grad,2.1,spin=0.5,accu=1.d-11,save=5102.1
cpmcscf, dgrad,1.1,2.1,    accu=1.d-11,save=5103.1
cpmcscf, nacm, 1.1,2.1,    accu=1.d-11,save=5104.1

forces;samc,5101.1;
forces;samc,5102.1;
forces;samc,5103.1;
forces;samc,5104.1;

```

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