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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           Marks all results as being out of date.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.

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. .IP "gbc" 1c This boolean specifies whether
       Generalized Brillouin Condition (GBC) is assumed to hold. The default
       istrue. 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 Moller-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 Moller-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 Moller-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.

   int sc::MBPT2_R12::value_implemented () const [virtual]
       Information about the availability of values, gradients, and hessians.

       Reimplemented from sc::MBPT2.

Author

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