[molpro-user] Getting rid of limit of 32 active orbitals in molpro2012.1

Nike Dattani dattani.nike at gmail.com
Fri May 26 02:16:10 CEST 2017

> Dear Sham,

> I believe in addition to the methods you mentioned, the limit also applies
to ACPF and AQCC. Just like Evgeniy wrote below, I would also be very
pleased to be able to have more than 32 orbitals active, and certainly the
RAM on some machines would allow much more than 32. Is the limit highly
non-trivial to increase in a future version, due to some hard-coded limits
imposed by using int32 instead of int64, meaning the density matrices can
have at most 2^32-1 elements?

If there is a foreseeable way to increase the limit, I would be very
delighted to try it out.

With best wishes!
Nike Dattani

> > Message: 2Date: Wed, 24 May 2017 11:29:35 +0200
> From: Sham K <shaawm at gmail.com>
> To: Evgeniy Gromov <evgeniy.gromov at pci.uni-heidelberg.de>
> Cc: molpro-user at molpro.net
> Subject: Re: [molpro-user] Getting rid of limit of 32 active orbitals
>         in      molpro2012.1
> Message-ID:
>         <CAMu9eMJ2CUTYRDo2+QhQ7zk+VmtX4woAf90a3VkDdah++nQKMg@
> mail.gmail.com>
> Content-Type: text/plain; charset="utf-8"
> Dear Evgeniy,
> There is no compiler option for this. The limit of 32 correlated internal
> orbitals (closed + active) exist for methods RS2 and MRCI in molpro. Two
> new related methods, RS2C and MRCIC, have been also available in molpro.
> For these programs, the limit is now 32 active orbitals and there is no
> limit on number of closed orbitals. The new MRCIC program works only for
> one state (typically ground state with multi-reference character).
> You can use them with {rs2c;...} or {mrcic;...} just like old programs.
> Best,
> Sham
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