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NAME

       sc::MBPT2_R12 - The MBPT2_R12 class implements several linear R12 second-order
       perturbation theory methods.

SYNOPSIS

       #include <mbptr12.h>

       Inherits sc::MBPT2.

   Public Member Functions
       MBPT2_R12 (StateIn &)
       MBPT2_R12 (const Ref< KeyVal > &)
           The KeyVal constructor.
       void save_data_state (StateOut &)
           Save the base classes (with save_data_state) and the members in the same order that
           the StateIn CTOR initializes them.
       Ref< GaussianBasisSet > aux_basis () const
       Ref< GaussianBasisSet > vir_basis () const
       bool gbc () const
       bool ebc () const
       LinearR12::ABSMethod abs_method () const
       LinearR12::StandardApproximation stdapprox () const
       bool spinadapted () const
       R12IntEvalInfo::StoreMethod r12ints_method () const
       const std::string & r12ints_file () const
       double corr_energy ()
       double r12_corr_energy ()
       RefSymmSCMatrix density ()
           Returns the SO density.
       void obsolete ()
           Marks all results as being out of date.
       int gradient_implemented () const
       int value_implemented () const
           Information about the availability of values, gradients, and hessians.
       void print (std::ostream &o=ExEnv::out0()) const
           Print information about the object.

   Protected Member Functions
       void compute ()
           Recompute at least the results that have compute true and are not already computed.

   Additional Inherited Members

Detailed Description

       The MBPT2_R12 class implements several linear R12 second-order perturbation theory
       methods.

Constructor & Destructor Documentation

   sc::MBPT2_R12::MBPT2_R12 (const Ref< KeyVal > &)
       The KeyVal constructor.

       gbc
           This boolean specifies whether Generalized Brillouin Condition (GBC) is assumed to
           hold. The default is 'true'. This keyword is only valid if stdapprox=A'. The effect of
           setting this keyword to true is rather small -- hence it is not recommended to use
           this keyword.

       ebc
           This boolean specifies whether Extended Brillouin Condition (EBC) is assumed to hold.
           The default is 'true'. This keyword is only valid if stdapprox=A'. The effect of
           setting this keyword to true is rather small -- hence it is not recommended to use
           this keyword.

       stdapprox
           This gives a string that must take on one of the values below. The default is A'.

       A   Use second order M/ller-Plesset perturbation theory with linear R12 terms in standard
           approximation A (MP2-R12/A). Only energies can be computed with the MP2-R12/A method.

       A'  Use second order M/ller-Plesset perturbation theory with linear R12 terms in standard
           approximation A' (MP2-R12/A'). This will cause MP2-R12/A energies to be computed also.
           Only energies can be computed with the MP2-R12/A' method.

       B   Use second order M/ller-Plesset perturbation theory with linear R12 terms in standard
           approximation B. This method is not implemented yet.

       spinadapted
           This boolean specifies whether to compute spin-adapted or spin-orbital pair energies.
           Default is to compute spin-adapted energies.

       aux_basis
           This specifies the auxiliary basis to be used for the resolution of the identity.
           Default is to use the same basis as for the orbital expansion.

       vir_basis
           This specifies the basis to be used for the virtual orbitals. Default is to use the
           same basis as for the orbital expansion.

       include_mp1
           This specifies whether to compute MP1 correction to the MP2 and MP2-R12 energies. This
           option only has effect if vir_basis is not the same as basis. MP1 correction is a
           perturbative estimate of the difference between the HF energy computed in vir_basis
           and basis. Usually, it is a very poor estimate -- therefore this keyword should be
           avoided by non-experts. Default is false.

       abs_method
           This string specifies whether the old ABS method, introduced by Klopper and Samson, or
           the new ABS variant, CABS, introduced by Valeev, should be used. Valid values are
           'ABS' (Klopper and Samson), 'ABS+', 'CABS', and 'CABS+', where the '+' labels a method
           where the union of OBS and ABS is used to construct the RI basis. The default is
           'ABS'. The default in 2.3.0 and later will be 'CABS+'.

       lindep_tol
           The tolerance used to detect linearly dependent basis functions in the RI basis set.
           The precise meaning depends on the orthogonalization method. The default value is
           1e-8.

       r12ints
           This specifies how to store transformed MO integrals. Valid values are:

       mem-posix
           Store integrals in memory for single-pass situations and in a binary file on task 0's
           node using POSIX I/O for multipass situations. posix is usually less efficient than
           mpi for distributed parallel multipass runs since the I/O is performed by one task
           only. However, this method is guaranteed to work in all types of environments, hence
           mem-posix is the default.

       posix
           Store integrals in a binary file on task 0's node using POSIX I/O. This method is
           different from mem-posix in that it forces the integrals out to disk even if they
           could be stored in memory. posix should only be used for benchmarking and testing
           purposes.

       mem-mpi
           Store integrals in memory for single-pass situations and in a binary file using MPI-
           I/O for multipass situations. This method assumes the availability of MPI-I/O. mem-mpi
           is the preferred choice in distributed environments which have MPI-I/O available.

       mpi
           Store integrals in a binary file using MPI-I/O. This method is different from mem-mpi
           in that it forces the integrals out to disk even if they could be stored in memory.
           mpi should only be used for benchmarking and testing purposes.

       mem
           Store integrals in memory. Can only be used with single-pass transformations for
           MP2-R12/A and MP2-R12/A' methods. This method should only be used for testing
           purposes.

       If r12ints is not specified, then mem-posix method will be used. If user wishes to use
       MPI-I/O, pending its availability, for higher parallel efficiency, r12ints should be
       explicitly set to mem-mpi.

       r12ints_file
           This specifies the prefix for the transformed MO integrals file if r12ints is set to
           posix, mpi, mem-posix or mem-mpi is used. Default is './<i>inputbasename</i>.r12ints',
           where inputbasename is the name of the input file without '.in'. If MPI-I/O is used
           then it is user's responsibility to ensure that the file resides on a file system that
           supports MPI-I/O.

       twopdm_grid_aa
           This optional keyword specifies a TwoBodyGrid object which to use for coordinates at
           which to compute alpha-alpha part of 2-PDM.

       twopdm_grid_ab
           This optional keyword specifies a TwoBodyGrid object which to use for coordinates at
           which to compute alpha-beta part of 2-PDM.

Member Function Documentation

   void sc::MBPT2_R12::compute () [protected],  [virtual]
       Recompute at least the results that have compute true and are not already computed. This
       should only be called by Result's members.

       Reimplemented from sc::MBPT2.

   void sc::MBPT2_R12::obsolete () [virtual]
       Marks all results as being out of date. Any subsequent access to results will cause
       Compute::compute() to be called.

       Reimplemented from sc::MBPT2.

   void sc::MBPT2_R12::save_data_state (StateOut &) [virtual]
       Save the base classes (with save_data_state) and the members in the same order that the
       StateIn CTOR initializes them. This must be implemented by the derived class if the class
       has data.

       Reimplemented from sc::MBPT2.

Author

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