arXiv subjects

Johannes Hauskrecht

Publications and source records attributed to Johannes Hauskrecht.

5 recordsLinked to original sources

arXiv2026

First application of the transcorrelated method to noncovalent interactions: The A24 dataset

We present the first application of transcorrelated (TC) coupled-cluster (CC) theory to noncovalent interactions within the xTC approximation. The method is assessed for the A24 dataset of hydrogen-bonded, mixed and pure dispersion bound dimers. The xTC interaction energies are computed at the CCSD, DCSD, and CCSD(T) levels in aug-cc-pVDZ (AVDZ), aug-cc-pVTZ (AVTZ) basis sets, and are compared with both canonical and explicitly correlated F12 methods. Because non-covalent interaction energies rely on delicate error cancellation between dimers and monomers, we optimize the TC Jastrow factor for each dimer, and reuse the same parameters for the corresponding monomer calculations. This shared-parameter strategy reduces stochastic optimization noise which would otherwise dominate the interaction energies. The results show that the xTC-CCSD(T)/AVTZ method performs extremely well for the hydrogen-bonded systems, with a mean-absolute error of only 0.007 kcal/mol in the interaction energies, with respect to the benchmark values generated with CCSD(T)/CBS + $Δ$CCSDT(Q) + core corrections. For pure dispersion bound systems the errors are slightly larger (0.055 kcal/mol), leading to an overall MAE of 0.030 kcal/mol for the entire dataset. Adding a $Δ$MP2 correction to the xTC-CCSD(T)/AVDZ brings these results close to AVTZ quality and provides a practical route toward larger noncovalent systems. A decomposition of the xTC interaction energy into a mean-field and correlation contribution shows that part of the correlation contribution is systematically shifted by the TC method to the mean-field contribution. This physically appealing feature indicates that the TC method has great potential for the quantitative description of noncovalent interactions, and opens a new route for high-accuracy quantum chemistry to be applied to systems of biological and soft-matter interest.

physics.chem-ph↗

arXiv2026

Compression of virtual spaces in transcorrelated methods via singular value decomposition: application to the G2 set

We introduce a new singular-value-decomposition-based scheme for constructing small virtual spaces out of large basis sets for transcorrelated (TC) calculations, termed SVD-TC. This work builds on the recent finding that the residual basis error in the TC reference energy converges more slowly than that of the correlation energy. Within the new workflow, the post Hartree-Fock TC calculation is performed in a compressed virtual orbital subspace, obtained by projecting the canonical virtual orbitals from a large basis set onto a smaller basis set through singular value decomposition (SVD). This allows us to achieve the high accuracy allowed by the large basis, whilst the bottleneck steps - TC integral calculation and post-HF correlation method such as CCSD(T) - incur the cost of only a small virtual space calculation. The method therefore is highly efficient, whilst avoiding the composite nature of the reference correction method. Using the new scheme, we widen the scope of benchmark-quality TC results into more complex molecules than previously considered: using the G2-1 set of 55 molecules with first- and second-row atoms, we apply SVD-xTC-CCSD(T) to compute atomization energies. We compare our results against the near-exact semistochastic heat-bath configuration interaction (SHCI) reference values and experiment. We find that SVD-xTC-CCSD(T) delivers chemical accuracy already with triple-$ζ$ basis sets. Finally, we use the quadruple-$ζ$ results to analyze the accuracy of pseudopotentials within the TC method, and show that pseudopotential TC workflow provides faster basis-set convergence than all-electron TC. We also present timings for computing the atomization energies on G2-1 set, demonstrating the efficiency of our TC workflows.

physics.chem-ph↗

arXiv2026

An Additive Reference Correction Scheme for the Transcorrelated Method

We introduce an additive reference correction for the transcorrelated (TC) method and its three-body mean-field approximation (xTC), to improve energy differences computed in small orbital basis sets. The correction is motivated by the observation that, for xTC atomization energies, the dominant error in double-ζ bases originates from the reference contribution rather than from the correlation energy. In the proposed reference-corrected scheme (RC-xTC), the small-basis correlation energy is retained, while the corresponding TC reference energy is replaced by its value from a larger basis. Benchmark calculations for the non-relativistic HEAT set with the Dunning basis-set family show that RC-xTC substantially improves both total and atomization energies relative to standard xTC in double-ζ bases. At the CCSD(T) level, RC-xTC yields better atomization energies than CCSD(T)-F12a in the double-ζ regime, while preserving the favorable total-energy accuracy of xTC. At the CCSD level, RC-xTC improves atomization energies relative to F12a throughout the full basis-set sequence. As the basis set is enlarged, xTC and RC-xTC become progressively identical, as expected from the construction of the correction.

physics.chem-ph↗

arXiv2025

A Transcorrelated Wave-Function Framework for Solids: An Application to Bulk and Defected Silicon

Accurate wave-function descriptions of pristine and defected solids remain challenging due to the simultaneous presence of finite-size, basis-set, and correlation errors. While embedding techniques alleviate finite-size effects and correlated wave-function approaches systematically improve correlation, basis-set incompleteness continues to limit practical accuracy. Here we present a study of transcorrelated (TC) many-body wave-function methods on properties of solid state systems. We augment the existing xTC theory to periodic systems, and establish an unified transcorrelated embedding framework that integrates periodic TC theory with fragment-based correlated solvers. Using silicon as a test case, we validate the method against coupled-cluster, FCIQMC, and diffusion Monte Carlo benchmarks for bulk. Then we apply TC embedding to calculation of formation energies of two silicon self-interstitials. The TC Hamiltonian yields rapid basis convergence and quantitatively reliable defect formation energies at the triple-$ζ$ level, substantially reducing the basis-set bottleneck for wave-function treatments of crystalline defects.

cond-mat.mtrl-sci↗

arXiv2025

Modular Construction of Jastrow Factors for the Transcorrelated Method

In this work, we explore the reuse of terms in the Jastrow factor between systems for use in the transcorrelated method, to reduce the number of optimisable parameters for a given system. In particular, we propose a workflow in which atom-specific parts of Jastrow factors, optimised in atoms, may be reused in the molecule, with only a few parameters in the electron-electron part of the Jastrow left to optimise, while maintaining performance. We find that the modified workflow not only reduces the number of terms needing to be optimised, but also improves the accuracy of xTC-CCSD(T) energies.

physics.chem-ph↗