Fast local-MP2 method with density-fitting for crystals. I. Theory and algorithms

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An efficient local coupled cluster method with single and double excitation operators and perturbative treatment of triple excitations [DF-LCCSD(T)] is described. All required two-electron integrals are evaluated using density fitting approximations. These have a negligible effect on the accuracy but reduce the computational effort by 1-2 orders of magnitude, as compared to standard integral-direct methods. Excitations are restricted to local subsets of non-orthogonal virtual orbitals (domain approximation). Depending on distance criteria, the correlated electron pairs are classified into strong, close, weak, and very distant pairs. Only strong pairs, which typically account for more than 90% of the correlation energy, are optimized in the LCCSD treatment. The remaining close and weak pairs are approximated by LMP2 (local second-order Møller-Plesset perturbation theory); very distant pairs are neglected. It is demonstrated that the accuracy of this scheme can be significantly improved by including the close pair LMP2 amplitudes in the LCCSD equations, as well as in the perturbative treatment of the triples excitations. Using this ansatz for the wavefunction, the evaluation and transformation of the two-electron integrals scale cubically with molecular size. If local density fitting approximations are activated, this is reduced to linear scaling. The LCCSD iterations scale quadratically, but linear scaling can be achieved by neglecting some terms involving contractions of single excitations. The accuracy and efficiency of the method is systematically tested using various approximations, and calculations for molecules with up to 90 atoms and 2636 basis functions are presented.

Section: B 3-and 4-external Integralsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

An efficient local coupled cluster method for accurate thermochemistry of large systems

Werner

Schütz

2011

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“…In particular, MP2 describes in a qualitatively correct way the dispersive interaction at long range. The implementation of fast integral evaluation techniques such as density fitting 4,[6][7][8][9][10] mean that the computational cost of a MP2 calculation is now not significantly higher than that of an HF or DFT calculation. Two other methods have been recently proposed to approximate the dispersive contribution.…”

Section: Introductionmentioning

confidence: 99%

Periodic quantum mechanical simulation of the He–MgO(100) interaction potential

Martínez-Casado

Mallia

Usvyat

et al. 2011

He-atom scattering is a well established and valuable tool for investigating surface structure. The correct interpretation of the experimental data requires an accurate description of the He-surface interaction potential. A quantum-mechanical treatment of the interaction potential is presented using the current dominant methodologies for computing ground state energies (Hartree-Fock, local and hybrid-exchange density functional theory) and also a novel post-Hartree-Fock ab initio technique for periodic systems (a local implementation of Møller-Plesset perturbation theory at second order). The predicted adsorption well depth and long range behavior of the interaction are compared with that deduced from experimental data in order to assess the accuracy of the interaction potential.

“…For semiconductor crystals, we selected the domains in order to take into account six tetrahedral units for a total amount of 26 atoms around each bond orbital. The maximum pair distance considered for the evaluation of MP2 correlation energy was fixed at 12 Å. Two-electron integrals within this range are evaluated efficiently in C either by density fitting 78,80,81 or multipolar expansion techniques-if the inter-orbital distance exceeds 8 Å.…”

Section: B Parameters Of the Calculationsmentioning

confidence: 99%

“…The K lr ia,jb integrals are efficiently evaluated through a robust 77 density-fitting scheme, suitably adapted for periodic systems. [78][79][80][81] By introducing an auxiliary basis set of Gaussiantype functions-here indicated by indices P and Q-the integrals are approximated as…”

Section: B Periodic Long-range Local Second-order Møller-plesset Cormentioning

confidence: 99%

Range-separated double-hybrid density-functional theory applied to periodic systems

Sansone

Civalleri

Usvyat

et al. 2015

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Articles you may be interested inBasis convergence of range-separated density-functional theory J. Chem. Phys. 142, 074107 (2015) Quantum chemistry methods exploiting density-functional approximations for short-range electronelectron interactions and second-order Møller-Plesset (MP2) perturbation theory for long-range electron-electron interactions have been implemented for periodic systems using Gaussian-type basis functions and the local correlation framework. The performance of these range-separated double hybrids has been benchmarked on a significant set of systems including rare-gas, molecular, ionic, and covalent crystals. The use of spin-component-scaled MP2 for the long-range part has been tested as well. The results show that the value of µ = 0.5 bohr −1 for the range-separation parameter usually used for molecular systems is also a reasonable choice for solids. Overall, these range-separated double hybrids provide a good accuracy for binding energies using basis sets of moderate sizes such as cc-pVDZ and aug-cc-pVDZ. C 2015 AIP Publishing LLC. [http://dx