Search for: All records

We present a fast, asymptotically linear-scaling implementation of the perturbative quadruples energy correction in coupled-cluster theory using local natural orbitals. Our work follows the domain-based local pair natural orbital (DLPNO) approach previously applied to lower levels of excitations in coupled-cluster theory. Our DLPNO-CCSDT(Q) algorithm uses converged doubles and triples amplitudes from a preceding DLPNO-CCSDT computation to compute the quadruples amplitude and energy in the quadruples natural orbital (QNO) basis. We demonstrate the compactness of the QNO space, showing that more than 95% of the (Q) correction can be recovered using relatively loose natural orbital cutoffs, compared to the tighter cutoffs used in pair and triples natural orbitals at lower levels of coupled-cluster theory. We also highlight the accuracy of our algorithm in the computation of relative energies, which yields deviations of sub-kJ mol−1 in relative energy compared to the canonical CCSDT(Q). Timings are conducted on a series of growing linear alkanes (up to 10 carbons and 608 basis functions) and water clusters (up to 49 water molecules and 2842 basis functions) to establish the asymptotic linear-scaling of our DLPNO-(Q) algorithm. 

What's Changed Optimize some vector operations by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/90 Add a way to create a tensor view of a pointer by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/92 Add python bindings by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/87 Update IndexUtils.hpp by @jturney in https://github.com/Einsums/Einsums/pull/95 Einsums Restructuring by @jturney in https://github.com/Einsums/Einsums/pull/97 Fix print. by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/102 Docs: Docs were not deploying by @jturney in https://github.com/Einsums/Einsums/pull/104 Fix performance issues by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/107 Fix parsing bug by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/110 Fix performance again by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/111 Fixing docs by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/101 Docs: Tweaks for consistency. by @jturney in https://github.com/Einsums/Einsums/pull/120 Move Design Patterns by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/121 Full Changelog: https://github.com/Einsums/Einsums/compare/v0.6.1...v1.0.0 

What's Changed Fix a missing typename on svd. by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/148 Full Changelog: https://github.com/Einsums/Einsums/compare/v1.0.1...v1.0.2 

Bring in fixes for Python builds. Full Changelog: https://github.com/Einsums/Einsums/compare/v1.0.2...v1.0.3 

Full Changelog: https://github.com/Einsums/Einsums/compare/v1.0.0...v1.0.1 

What's Changed Fixed a typo by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/160 Bring indices into parity with devel. by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/166 Fixed a bug with the handling of block tensors in einsum by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/171 Update release version by @cgbriggs99 in https://github.com/Einsums/Einsums/pull/176 Full Changelog: https://github.com/Einsums/Einsums/compare/v1.0.3...v1.0.4 

We present an efficient, open-source formulation for coupled-cluster theory through perturbative triples with domain-based local pair natural orbitals [DLPNO-CCSD(T)]. Similar to the implementation of the DLPNO-CCSD(T) method found in the ORCA package, the most expensive integral generation and contraction steps associated with the CCSD(T) method are linear-scaling. In this work, we show that the t1-transformed Hamiltonian allows for a less complex algorithm when evaluating the local CCSD(T) energy without compromising efficiency or accuracy. Our algorithm yields sub-kJ mol−1 deviations for relative energies when compared with canonical CCSD(T), with typical errors being on the order of 0.1 kcal mol−1, using our TightPNO parameters. We extensively tested and optimized our algorithm and parameters for non-covalent interactions, which have been the most difficult interaction to model for orbital (PNO)-based methods historically. To highlight the capabilities of our code, we tested it on large water clusters, as well as insulin (787 atoms).