English (United Kingdom)

https://curated-unify.zendy.io/wp-json/zendy-region/v1/featured_content/oa?rat=en

https://curated-unify.zendy.io/wp-json/zendy-region/v1/highlighted_journal/

Global: Zendy Plus annual

Presents the access of premium content as premium feature

Premium Content

Presents the keyphrase highlighting as premium feature

Keyphrase Highlighting

Presents the summarisation as premium feature

Summarisation

Insights

Presents the pdf analysis as premium feature

PDF Analysis

Presents the zaia usage as premium feature

ZAIA

Global: Zendy Tools annual

Global: Zendy Free Plan

Global: Zendy Tools monthly

Global: Zendy Plus monthly

We employ quantum Monte Carlo to obtain chemically accurate vertical andadiabatic excitation energies, and equilibrium excited-state structures for thesmall, yet challenging, formaldehyde and thioformaldehyde molecules. A keyingredient is a robust protocol to obtain balanced ground- and excited-stateJastrow-Slater wave functions at a given geometry, and to maintain such abalanced description as we relax the structure in the excited state. We usedeterminantal components generated via a selected configuration interactionscheme which targets the same second-order perturbation energy correction forall states of interest at different geometries, and we fully optimize allvariational parameters in the resultant Jastrow-Slater wave functions.Importantly, the excitation energies as well as the structural parameters inthe ground and excited states are converged with very compact wave functionscomprising few thousand determinants in a minimally augmented double-$\zeta$basis set. These results are obtained already at the variational Monte Carlolevel, the more accurate diffusion Monte Carlo method yielding only a smallimprovement in the adiabatic excitation energies. We find that matchingJastrow-Slater wave functions with similar variances can yield excitationscompatible with our best estimates; however, the variance-matching procedurerequires somewhat larger determinantal expansions to achieve the same accuracy,and it is less straightforward to adapt during structural optimization in theexcited state.

Excited states with selected CI-QMC: chemically accurate excitation energies and geometries