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Higher-order coupled cluster methods like CCSDT and CCSDTQ show improved convergence with a new equation structure. This method enhances computational efficiency, especially for complex quantum chemistry calculations.

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Area of Science:

  • Quantum Chemistry
  • Computational Physics
  • Theoretical Chemistry

Background:

  • Higher-order coupled cluster (CC) methods, including CCSDT and CCSDTQ, often exhibit slower convergence compared to the standard coupled cluster singles and doubles (CCSD) method.
  • This convergence issue poses a significant challenge for accurate and efficient electronic structure calculations.

Purpose of the Study:

  • To analyze the convergence behavior of higher-order coupled cluster methods using Møller-Plesset perturbation theory.
  • To propose a novel computational approach for CCSDT and CCSDTQ that improves convergence rates and overall efficiency.

Main Methods:

  • Analysis of CCSDT and CCSDTQ equations through the lens of Møller-Plesset perturbation theory.
  • Development of a new equation structure that reorders contributions to cluster amplitudes.
  • Emphasis on incorporating lower-order energy corrections iteratively.
  • Numerical comparison against the direct inversion in the iterative subspace (DIIS) acceleration technique.

Main Results:

  • The proposed new structure for CCSDT and CCSDTQ equations demonstrates superior convergence compared to standard approaches.
  • Numerical tests show significant improvements in convergence rate and total time-to-solution.
  • The benefits are particularly pronounced for methods involving quadruple excitations.

Conclusions:

  • The reordered equation structure offers a more efficient pathway for higher-order coupled cluster calculations.
  • This advancement can accelerate complex quantum mechanical simulations, particularly in fields requiring high accuracy.
  • The findings suggest a practical improvement for computational chemistry and physics.