Perturbation Theory

Szabados, Ágnes

doi:10.1016/b978-0-12-409547-2.11467-2

Cited by 2 publications

(3 citation statements)

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“…While the accuracy of conventional MP2 does not reach that of the “gold standard” coupled-cluster (CC) model with single, double, and perturbative triple excitations [CCSD(T)], 7 , 8 its favorable computational cost motivated the development of various improved MP2-based methods. 9 , 10 Among those, the spin-component-scaled (SCS) MP2 schemes 11 − 15 and the double-hybrid (DH) density functionals, 16 − 19 both proposed by Grimme, have gained wide popularity. 15 , 18 In the SCS-MP2 methods, the opposite- and same-spin contributions to the correlation energy are scaled by different empirical factors, whereas for the DH functionals, the energy is augmented with an MP2-like second-order perturbation theory (PT2) correction evaluated on Kohn–Sham (KS) orbitals.…”

Section: Introductionmentioning

confidence: 99%

“…The importance and difficulties of the explicit treatment of electron correlation for such systems and the related processes are also well understood. ,, The second-order Møller–Plesset approach (MP2) is one of the standard tools for that purpose. While the accuracy of conventional MP2 does not reach that of the “gold standard” coupled-cluster (CC) model with single, double, and perturbative triple excitations [CCSD(T)], , its favorable computational cost motivated the development of various improved MP2-based methods. , Among those, the spin-component-scaled (SCS) MP2 schemes − and the double-hybrid (DH) density functionals, − both proposed by Grimme, have gained wide popularity. , In the SCS-MP2 methods, the opposite- and same-spin contributions to the correlation energy are scaled by different empirical factors, whereas for the DH functionals, the energy is augmented with an MP2-like second-order perturbation theory (PT2) correction evaluated on Kohn–Sham (KS) orbitals. The introduction of spin-scaled PT2 expressions into the formulation of DH functionals − turned out to be particularly successful to raise the accuracy of DH functionals above that of conventional density functionals. ,− …”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Linear-Scaling Open-Shell MP2 Approach: Algorithm, Benchmarks, and Large-Scale Applications

Szabó

Csóka

Kállay

et al. 2021

J. Chem. Theory Comput.

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A linear-scaling local second-order Møller–Plesset (MP2) method is presented for high-spin open-shell molecules based on restricted open-shell (RO) reference functions. The open-shell local MP2 (LMP2) approach inherits the iteration- and redundancy-free formulation and the completely integral-direct, OpenMP-parallel, and memory and disk use economic algorithms of our closed-shell LMP2 implementation. By utilizing restricted local molecular orbitals for the demanding integral transformation step and by introducing a novel long-range spin-polarization approximation, the computational cost of RO-LMP2 approaches that of closed-shell LMP2. Extensive benchmarks were performed for reactions of radicals, ionization potentials, as well as spin-state splittings of carbenes and transition-metal complexes. Compared to the conventional MP2 reference for systems of up to 175 atoms, local errors of at most 0.1 kcal/mol were found, which are well below the intrinsic accuracy of MP2. RO-LMP2 computations are presented for challenging protein models of up to 601 atoms and 11 000 basis functions, which involve either spin states of a complexed iron ion or a highly delocalized singly occupied orbital. The corresponding runtimes of 9–15 h obtained with a single, many-core CPU demonstrate that MP2, as well as spin-scaled MP2 and double-hybrid density functional methods, become widely accessible for open-shell systems of unprecedented size and complexity.

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