[Columbus] MCSCF in COLUMBUS

[Scott Brozell]

Hi,

In ciudg, at least in version 6, the external space cannot be
nonexistent; a known but easily forgotten detail.  See the tail
for an example.  When i want a FCI to compare to i use the
oldie-but-goodie cidbg.


On Thu, Mar 02, 2017 at 02:21:38PM +0100, Hans Lischka wrote:
> Dear Spiridoula,
> 
> In a FCI there are no orbitals to optimize since the energy is
> invariant under unitary transformations. The final reason of the
> breaking is the fact that there are no virtual orbitals, as you
> suspected. Actually, a simple energy calculation would be
> sufficient. I am not sure from the error message where the
> calculations really broke. Did it do so at the very beginning or did
> go beyond the energy calculation? Could yo send us the mcscfls file
> from the WORK directory?
> 
> The alternative is (as Felix wrote) to use the ciudg program and
> perform the FCI calculation with a corersponding reference space and
> zero excitations into the virtual (non-existent) space.
> 
> Ron and Thomas, do you have other suggestions?
> 
> Best regards, Hans
> 
> On 3/1/2017 8:46 PM, Spiridoula Matsika wrote:
> >Dear Columbus friends,
> >
> >I am trying to run a benchmark calculation. The system is HeH+ and I am
> >setting up an MCSCF to act as FCI. So the active space contains all the
> >orbitals in the basis set. But the calculation always fails. I have
> >tried different versions of Columbus, different basis sets, etc. but
> >nothing seems to work. The error I get is:
> >
> > *** error *** orthot: na,nb=         0         1
> > bummer (fatal):orthot: argument error                      0
> >
> >
> >Is there any reason that the MCSCF in COLUMBUS will not work if there
> >are no virtual orbitals and all orbitals are included in the CAS?

In version 6:
ciml.x < h8fci.cimlin
runc

=== ciudgls
...
     ********************************************
     **    PROGRAM:              CIUDG         **
     **    PROGRAM VERSION:      -varseg3-     **
     **    DISTRIBUTION VERSION: 6.0 beta8     **
     ********************************************

 using llenci=          -1
 fsize=      131040       16380
 bummer (fatal):inconsistent file size of ofdgint      4095
===

=== h8fci.cimlin

<ciml>

 <molecule>
  <description>
H8 D2h.  JCP 100 (1994) 5792.
  </description>
  <symmetry> d2h </symmetry>
<!--
Distort an octagon, side length a, of hydrogens by pulling on an opposite
set of sides to displace the sides equally outward by distance b.
     H3  H4
H2              H5

H1              H6
     H8  H7
-->
  <geometry>
   <units> bohr </units>
   <variable_assignment> a = 2.0 </variable_assignment>
	<variable_assignment> b = 1. </variable_assignment>
   <atomic_coordinate>
 H8  <triple> <x> -a*(1 + sqrt(2)) /2 </x> <y> -a /2                   </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H7  <triple> <x> -a*(1 + sqrt(2)) /2 </x> <y>  a /2                   </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H3  <triple> <x>  a*(1 + sqrt(2)) /2 </x> <y> -a /2                   </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H4  <triple> <x>  a*(1 + sqrt(2)) /2 </x> <y>  a /2                   </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H1  <triple> <x> -a /2               </x> <y> -b - a*(1 + sqrt(2)) /2 </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H2  <triple> <x>  a /2               </x> <y> -b - a*(1 + sqrt(2)) /2 </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H6  <triple> <x> -a /2               </x> <y>  b + a*(1 + sqrt(2)) /2 </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
   <atomic_coordinate>
 H5  <triple> <x>  a /2               </x> <y>  b + a*(1 + sqrt(2)) /2 </y> <z> 0.0 </z> </triple>
   </atomic_coordinate>
  </geometry>
 </molecule>

 <basis><standard> Huzinaga minimal; JCP 42(1965)1293.
 </standard></basis>
<!--
argos no p function lxyz bug
 <use_argos/>
-->

 <scf>
  <description>
H8 MBS.  1ag^2 1b2u^2 1b3u^2 2ag^2  1Ag State.
  </description>
  <initial_orbitals>
   <atomic_orbitals>
    <doubly_occupied> 1ag 1b2u 1b3u 2ag </doubly_occupied>
   </atomic_orbitals>
  </initial_orbitals>
  <convergence_tolerance_exponent> 11 </convergence_tolerance_exponent>
 </scf>

 <ci>
  <description>
H8 MBS.  1Ag FCI attempt.
  </description>
  <reference_space>
   <group_occupations> (1ag 1b2u 1b3u 2ag 1b1g 2b2u 2b3u 2b1g)^8 </group_occupations>
  </reference_space>
  <number_roots> 2 </number_roots>
  <convergence_tolerance> 1e-5 </convergence_tolerance>
 </ci>

</ciml>
===

scott