[molpro-user] Extended Multi-State CASPT2
Werner Győrffy
gyorffy at theochem.uni-stuttgart.de
Fri Jul 4 08:28:14 BST 2014
Dear Alan,
The answer to your question is that configurations are represented as
bit strings: 11110101... 1 for occupied orbitals and 0 for unoccupied
ones. In the 32-bit case, 32 spin orbitals = 16 spatial orbitals can be
represented this way. In the 64-bit case, this amounts to 32 spatial
orbitals.
Regards,
Werner.
On 07/03/2014 10:32 PM, Alan Chien wrote:
> Just a follow-up to my previous post.
>
> Based on a number of runs, and looking at the number of CSF's that come
> out, I've convinced myself that the double excitations are from the
> CLOSED-CORE orbitals to all virtuals.
>
> The definition of "active space" in Molpro's CASPT2 (RS2) program seems
> to just be specific to the RS2 program itself.
>
> The definition of active space for RS2 and RS2C is laid out in slightly
> clearer language in the "quickstart" portion of the online manual.
> http://www.molpro.net/info/2012.1/doc/quickstart/node24.html
> Quoted below in case the online manual changes in the future
>
> In case of rs2 and rs3, exactly the same configuration spaces as in
> the MRCI are used. In this case the excitations with two electrons
> in the external orbital space are /internally contracted/. The total
> number of correlated orbitals is restricted to 16 for machines with
> 32-bit integers and to 32 for machines with 64-bit integers.
>
> In the rs2c case certain additional configuration classes involving
> internal and semi-internal excitations are also internally
> contracted (see J. Chem. Phys. *112*, 5546 (2000)). This is exactly
> as in the mrcic case (see above). This method is much more efficient
> than rs2 and more suitable for large cases. In particular, in this
> case only the number of /active/ orbitals is restricted to 16 or 32
> on 32 and 64 bit machines, respectively, and any number of
> closed-shell (inactive) orbitals can be used (up to a maximum as
> defined by a program parameter).
>
> I've pretty much exhausted my questions on the limitations/capabilities
> of Molpro's CASPT2 program.
>
> Final question: Why is there a limit of 32 correlated orbitals in RS2? I
> fiddled with the source code a bit, and it doesn't seem to be just an
> arbitrary number set when the program was written - but the reason is
> not quite transparent from a brief look at the code in src/mrci/.
>
>
>
>
> On Wed, Jul 2, 2014 at 12:51 PM, Alan Chien <alandc at umich.edu
> <mailto:alandc at umich.edu>> wrote:
>
> Thank you for your reply Werner, its cleared up a lot of my initial
> questions.
> I had actually determined that there was a difference between CORE
> and FROZEN, but was still trying to figure things out a bit better.
>
> I have a few clarification questions. Please forgive the length, but
> I'm trying to be as precise as possible so that no further
> clarifications will be necessary, heh.
>
> For the CAS portion of CASPT2 (separate from the MULTI calc), the
> reference determinants are generated using the orbitals defined by
> OCC - CLOSED.
> For the PT2 portion, we have to define a space from which we can do
> doubles excitations, i.e. correlate certain orbitals. This is
> defined as those orbitals in CLOSED - CORE. _But how do we define
> where those double excitations go to_? Do they only go to the empty
> orbitals that we included in OCC? Or are they automatically allowed
> to be excited to any/all virtuals (Which seems unlikely since
> virtuals usually make up a large portion of the MOs).
>
> CASPT2 (RS2) defines "active space" as both the space used to create
> the CAS determinants _as well as_ the orbitals which we allow to be
> correlated.
> I find this strange as before now, I've only ever worked with
> CAS/RAS, and I'm used to thinking of active spaces as just the
> orbital set used to generate the set of reference determinants. Is
> this definition of active space a quirk of Molpro or is it the
> accepted standard when discussing CASPT2?
>
> Finally, does RS2C treat the CORE,CLOSED,OCC cards differently when
> making its definition of the "active space"? This link (which I
> posted earlier),
> http://www.molpro.net/pipermail/molpro-user/2006-April/001759.html,
> seems to suggest that it does. But I am unclear as to why that may
> be as the manual states that the RS2 and RS2C programs are
> essentially the same, just one is faster or has different features
> implemented compared to the other. Perhaps it is just a difference
> in the code of each program instead of a difference having any
> substantive meaning?
>
> I understand that some of these questions I can answer myself
> (namely the last one) with a couple of Molpro test jobs, and in lieu
> of provided answers, I may well determine them myself.
>
> But any help is welcome,
> Alan Chien
>
>
>
> On Wed, Jul 2, 2014 at 6:12 AM, Werner Győrffy
> <gyorffy at theochem.uni-stuttgart.de
> <mailto:gyorffy at theochem.uni-stuttgart.de>> wrote:
>
> Dear Alan,
>
> CLOSED orbitals are doubly occupied in all reference
> configurations but excitations are allowed from them in the
> CASPT2 calculations if they are not frozen. If you want to
> define orbitals which are frozen (not correlated) in CASPT2, you
> should use CORE orbitals. CORE orbitals are not counted for the
> 32 orbital limitation in the rs2 program.
>
> Active orbitals in CASSCF are defined as OCC minus CLOSED orbitals.
>
> An (X)MS-CASPT2 calculation is still possible only with the rs2
> program not with rs2c.
>
> Regards,
>
> Werner Gyorffy.
>
>
>
>
> On 07/01/2014 11:56 PM, Alan Chien wrote:
>
> Interesting nugget of information. The example given in the
> multi-state
> CASPT2 section of the manual DOES change its active space
> when you
> change the numbers in the closed card.
> So it seems that for that particular example it can
> recognize closed input.
>
> Example:
> http://www.molpro.net/info/__current/examples/lif_mr___mscaspt2.com
> <http://www.molpro.net/info/current/examples/lif_mr_mscaspt2.com>
> (I edited it so that it only did r=3 ang to reduce the amt
> of output I
> had to look at. Also removed everything below RS2 section)
>
> Trying to replicate it now. In fact, been trying for a while.
>
>
>
>
> On Tue, Jul 1, 2014 at 3:48 PM, Alan Chien <alandc at umich.edu
> <mailto:alandc at umich.edu>
> <mailto:alandc at umich.edu <mailto:alandc at umich.edu>>> wrote:
>
> Dear Molpro Community,
>
> I was wondering if there was something wrong with my
> following input
> for an extended multi-state CASPT2 calculation. My
> input is not
> recognizing the CLOSED card, and so is throwing the
> error "TOO MANY
> ACTIVE ORBITALS: 48 THIS VERSION ALLOWS 32." An old
> thread mentions
> that I should use RS2C -
> http://www.molpro.net/__pipermail/molpro-user/2006-__April/001759.html
> <http://www.molpro.net/pipermail/molpro-user/2006-April/001759.html>
> -
> which should recognize closed orbitals.
>
> But it's a rather old thread, and I want XMS-CASPT2
> which isn't
> implemented for RSC2, and so I thought it worth
> mentioning to see if
> they had updated the RS2 code and perhaps my input was
> just off. The
> manual makes no mention of RS2 being unable to
> recognize the CLOSED
> card. I also tried the same input with FROZEN and that
> threw the
> same error.
>
> Any input welcome,
> Alan Chien
>
>
> ***,title
> memory,400,m
> symmetry
> geometry={
> S 1.9692714536 0.9837700026
> 0.0000000000
> C 0.6745300892 -0.1941173367
> 0.0000000000
> C 1.1941024748 -1.4906632561
> 0.0000000000
> C 2.5920412491 -1.5265017306
> 0.0000000000
> C 3.1677860531 -0.2809638443
> 0.0000000000
> C -0.6745300892 0.1941173367
> 0.0000000000
> C -1.1941024748 1.4906632561
> 0.0000000000
> C -2.5920412491 1.5265017306
> 0.0000000000
> C -3.1677860531 0.2809638443
> 0.0000000000
> S -1.9692714536 -0.9837700026
> 0.0000000000
> C -4.5811338904 -0.0064991780
> 0.0000000000
> C -5.5229897499 1.0602944736
> 0.0000000000
> N -6.2538051640 <tel:2538051640>
> <tel:2538051640 <tel:2538051640>> 1.9321608642
>
> 0.0000000000
> C 4.5811338904 0.0064991780
> 0.0000000000
> C 5.5229897499 -1.0602944736
> 0.0000000000
> N 6.2538051640 <tel:2538051640>
> <tel:2538051640 <tel:2538051640>> -1.9321608642
>
> 0.0000000000
> C 5.0766433381 1.3388671764
> 0.0000000000
> N 5.4513787354 2.4133206959
> <tel:4133206959> <tel:4133206959 <tel:4133206959>>
>
> 0.0000000000
> C -5.0766433381 -1.3388671764
> 0.0000000000
> N -5.4513787354 -2.4133206959
> <tel:4133206959> <tel:4133206959 <tel:4133206959>>
> 0.0000000000
> H -3.1636666579 2.4343293653
> <tel:4343293653> <tel:4343293653 <tel:4343293653>>
> 0.0000000000
> H -0.5803308458 <tel:5803308458>
> <tel:5803308458 <tel:5803308458>> 2.3697711304
> 0.0000000000
> H 0.5803308458 <tel:5803308458>
> <tel:5803308458 <tel:5803308458>> -2.3697711304
> 0.0000000000
> H 3.1636666579 -2.4343293653
> <tel:4343293653> <tel:4343293653 <tel:4343293653>>
>
> 0.0000000000
> }
>
> basis=6-31G*
> hf
> {casscf;
> closed,31,6,30,5 !core orbs, total 72
> occ,31,8,30,7 !active orbs, total 76
> wf,148,1,0;state,2
> wf,148,3,0
> pspace,100.0
> }
>
> {rs2,xms=1,mix=2;
> state,2,2,3
> }
>
>
>
>
>
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