Communication: The distinguishable cluster approximation.

We present a method that accurately describes strongly correlated states and captures dynamical correlation. It is derived as a modification of coupled-cluster theory with single and double excitations (CCSD) through consideration of particle distinguishability between dissociated fragments, whilst retaining the key desirable properties of particle-hole symmetry, size extensivity, invariance to rotations within the occupied and virtual spaces, and exactness for two-electron subsystems. The resulting method, called the distinguishable cluster approximation, smoothly dissociates difficult cases such as the nitrogen molecule, with the modest N(6) computational cost of CCSD. Even for molecules near their equilibrium geometries, the new model outperforms CCSD. It also accurately describes the massively correlated states encountered when dissociating hydrogen lattices, a proxy for the metal-insulator transition, and the fully dissociated system is treated exactly.

[1]  Monika Musiał,et al.  Addition by subtraction in coupled-cluster theory: a reconsideration of the CC and CI interface and the nCC hierarchy. , 2006, The Journal of chemical physics.

[2]  M. Head‐Gordon,et al.  A fifth-order perturbation comparison of electron correlation theories , 1989 .

[3]  T. Crawford,et al.  An Introduction to Coupled Cluster Theory for Computational Chemists , 2007 .

[4]  Marcel Nooijen,et al.  pCCSD: parameterized coupled-cluster theory with single and double excitations. , 2010, The Journal of chemical physics.

[5]  Jürgen Gauss,et al.  State‐specific multireference coupled‐cluster theory , 2013 .

[6]  Karol Kowalski,et al.  The method of moments of coupled-cluster equations and the renormalized CCSD[T], CCSD(T), CCSD(TQ), and CCSDT(Q) approaches , 2000 .

[7]  Rodney J. Bartlett,et al.  Molecular Applications of Coupled Cluster and Many-Body Perturbation Methods , 1980 .

[8]  P. Knowles,et al.  An efficient internally contracted multiconfiguration–reference configuration interaction method , 1988 .

[9]  Anton V. Sinitskiy,et al.  Strong correlation in hydrogen chains and lattices using the variational two-electron reduced density matrix method. , 2010, The Journal of chemical physics.

[10]  Sandeep Sharma,et al.  The density matrix renormalization group in quantum chemistry. , 2011, Annual review of physical chemistry.

[11]  Wilfried Meyer,et al.  Ionization energies of water from PNO‐CI calculations , 2009 .

[12]  Anna I. Krylov,et al.  Size-consistent wave functions for bond-breaking: the equation-of-motion spin-flip model , 2001 .

[13]  Hans-Joachim Werner,et al.  A comparison of the efficiency and accuracy of the quadratic configuration interaction (QCISD), coupled cluster (CCSD), and Brueckner coupled cluster (BCCD) methods , 1992 .

[14]  F. Neese,et al.  Efficient and accurate local approximations to coupled-electron pair approaches: An attempt to revive the pair natural orbital method. , 2009, The Journal of chemical physics.

[15]  Hans-Joachim Werner,et al.  Simplified CCSD(T)-F12 methods: theory and benchmarks. , 2009, The Journal of chemical physics.

[16]  R. Mirman.  Experimental meaning of the concept of identical particles , 1973, Il Nuovo Cimento B.

[17]  Martin Head-Gordon,et al.  A fusion of the closed-shell coupled cluster singles and doubles method and valence-bond theory for bond breaking. , 2012, The Journal of chemical physics.

[18]  P. Knowles,et al.  Approximate variational coupled cluster theory. , 2011, The Journal of chemical physics.

[19]  G. Scuseria,et al.  Strong correlations via constrained-pairing mean-field theory. , 2009, The Journal of chemical physics.

[20]  Josef Paldus,et al.  Approximate account of the connected quadruply excited clusters in the coupled-pair many-electron theory , 1984 .

[21]  Martin Head-Gordon,et al.  Benchmark variational coupled cluster doubles results , 2000 .

[22]  R. Nesbet.  Brueckner's Theory and the Method of Superposition of Configurations , 1958 .

[23]  Martin Schütz,et al.  Molpro: a general‐purpose quantum chemistry program package , 2012 .

[24]  D. Mukherjee,et al.  Correlation problem in open-shell atoms and molecules. A non-perturbative linked cluster formulation , 1975 .

[25]  Josef Paldus,et al.  Coupled Cluster Approach , 1980 .

[26]  M. Head‐Gordon,et al.  Highly correlated calculations with a polynomial cost algorithm: A study of the density matrix renormalization group , 2002 .

[27]  White,et al.  Density matrix formulation for quantum renormalization groups. , 1992, Physical review letters.

[28]  Isaiah Shavitt,et al.  Many-Body Methods in Chemistry and Physics: MBPT and Coupled-Cluster Theory , 2009 .

[29]  J. Cizek.  On the Correlation Problem in Atomic and Molecular Systems. Calculation of Wavefunction Components in Ursell-Type Expansion Using Quantum-Field Theoretical Methods , 1966 .