CCL: New ORCA Version Released

[Frank Neese <neese!^!thch.uni-bonn.de>]

 Sent to CCL by: Frank Neese [neese[]thch.uni-bonn.de]
 Dear CCL'ers,
today we have released the latest version of the ORCA electronic
 structure program. It is free for academic users and can be
 downloaded from our website  http://www.thch.uni-bonn.de/tc/orca/.
 The present version (2.6.00) has significantly enhanced
 functionality. Specifically:
 - Parallelism has been re-installed.
- Implementation of highly correlated single reference methods (so
 far only for closed shell ground states)
        * CCSD and CCSD(T)
        * QCISD and QCISD(T)
        * CPF and CEPA methods
   the rate limiting step involving the "four external"
 integrals
 can either be done via a full integral transformation,
    the RI approximation or in an AO direct way. The code is flexible
 and efficient. A spin unrestricted version
    is in preparation.
- Efficient implementation of Head-Gordon's doubles correction to CIS
 (CIS(D) method). It is implemented
    in ORCA for excited states via the RI approximation. Using
 transformed RI integrals, the speed of the
    preceeding CIS calculation has been vastly improved compared to
 the previous AO based implementation
    (the use of transformed integrals is optional of course). Systems
 with up to ~1000 basis functions were
    succesfully treated with this code.
- We have completely re-worked the geometry optimizer. Optimizations
 are more robust now and usually converge
    in fewer cycles. It is now possible to impose user defined
 constraints in internal coordinates and also to perform
    relaxed surface scans. Transition state finding is coming in a
 subsequent release. The starting Hessian can
    now be read from a previous optimization of frequency calculation
 and can be used to improve the convergence
    of optimization runs (e.g. a semi-empirical or small-basis set
 RI-DFT Hessian could be used).
- The performance of canonical MP2 calculations has been improved, in
 particular for larger systems.
- Stefan Grimme's dispersion corrections for a variety of DFT
 functionals and also for the new
    double hybrids B2PLYP and mPW2PLYP.
- Last but not least, as usual, we have fixed the bugs that came to
 our attention.
- A number of additional features have been implemented and will be
 documented following the publication of
    the original research.
 We hope that you enjoy the program!
 Best regards,
 Frank Neese and Frank Wennmohs on behalf of the ORCA development team