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Calling Sequence
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MP2(molecule, options)
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Parameters
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molecule
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list of lists; each list has 4 elements, the string of an atom's symbol and atom's x, y, and z coordinates
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options
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(optional) equation(s) of the form option = value where option is one of symmetry, unit, max_memory, nuclear_gradient, return_rdm, populations, conv_tol_hf, diis_hf, diis_space_hf, diis_start_cycle_hf, direct_scf_hf, direct_scf_tol_hf, level_shift_hf, max_cycle_hf, max_memory_scf_hf, nuclear_gradient_hf, populations_hf
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Description
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Second-order many-body perturbation theory (MP2) computes the ground state of a many-electron atom or molecule with the correlation energy treated by a second-order perturbation expansion around the Hartree-Fock energy.
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MP2 is non-variational, meaning that its energy is not necessarily an upper bound to the full CI energy in a given basis set.
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Outputs
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The table of following contents:
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float -- total electronic energy of the system
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float -- the difference between the MP2 energy and the Hartree-Fock energy
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Matrix -- coefficients expressing molecular orbitals (columns) in terms of atomic orbitals (rows)
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Vector -- molecular orbital occupations
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Array -- two-electron transition amplitudes
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Matrix -- one-particle reduced density matrix (1-RDM) in molecular-orbital (MO) representation
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Array -- two-particle reduced density matrix (2-RDM) in molecular-orbital (MO) representation
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Matrix -- analytical nuclear gradient
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Vector -- dipole moment according to its x, y and z components
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Matrix -- atomic-orbital populations
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Vector -- atomic charges from the populations
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Options
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basis = string -- name of the basis set. See Basis for a list of available basis sets. Default is "sto-3g".
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spin = nonnegint -- twice the total spin S (= 2S). Default is 0.
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charge = nonnegint -- net charge of the molecule. Default is 0.
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symmetry = string/boolean -- is the Schoenflies symbol of the abelian point-group symmetry which can be one of the following: D2h, C2h, C2v, D2, Cs, Ci, C2, C1. true finds the appropriate symmetry while false (default) does not use symmetry.
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unit = string -- "Angstrom" or "Bohr". Default is "Angstrom".
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max_memory = posint -- allowed memory in MB. Default is 4000.
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ghost = list of lists -- each list has the string of an atom's symbol and the atom's x, y, and z coordinates. See Ghost Atoms.
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initial_mo = Matrix -- Matrix of MOs (columns) in terms of atomic orbitals (rows) that defines the MO basis set.
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nuclear_gradient = boolean -- option to return the analytical nuclear gradient if available. Default is false.
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return_rdm = string -- options to return the 1-RDM and/or 2-RDM: "none", "rdm1", "rdm1_and_rdm2". Default is "rdm1".
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populations = string -- atomic-orbital population analysis: "Mulliken" and "Mulliken/meta-Lowdin". Default is "Mulliken".
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Attributes for Hartree Fock:
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conv_tol_hf = float -- converge threshold. Default is
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diis_hf = boolean -- whether to employ diis. Default is true.
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diis_space_hf = posint -- diis's space size. By default, 8 Fock matrices and error vectors are stored.
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diis_start_cycle_hf = posint -- the step to start diis. Default is 1.
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direct_scf_hf = boolean -- direct SCF in which integrals are recomputed is used by default.
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direct_scf_tol_hf = float -- direct SCF cutoff threshold. Default is
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level_shift_hf = float/int -- level shift (in au) for virtual space. Default is
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max_cycle_hf = posint -- max number of iterations. Default is 50.
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max_memory_scf_hf = posint -- allowed memory in MB. Default is 4000.
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nuclear_gradient_hf = boolean -- option to return the analytical nuclear gradient. Default is false.
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populations_hf = string -- atomic-orbital population analysis: "Mulliken" and "Mulliken/meta-Lowdin". Default is "Mulliken".
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References
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2.
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A. Szabo and N. S. Ostlund, Modern Quantum Chemistry: Introduction to Advanced Electronic Structure Theory (Dover Books, New York, 1996).
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Examples
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An MP2 calculation of the molecule
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