Analytical energy gradients for explicitly correlated wave functions. II. Explicitly correlated coupled cluster singles and doubles with perturbative triples corrections: CCSD(T)-F12

Abstract

We present an implementation of analytical energy gradients for the explicitly correlated coupled cluster singles and doubles method with perturbative triples corrections [CCSD(T)-F12]. The accuracy of the CCSD(T)-F12 analytical gradient technique is demonstrated by computing equilibrium geometries for a set of closed-shell molecules containing first- and second-row elements. Near basis-set limit equilibrium geometries are obtained with triple-zeta correlation consistent basis sets. Various approximations in the F12 treatment are compared, and the effects of these are found to be small.

Quantum-chemistry-aided identification, synthesis and experimental validation of model systems for conformationally controlled reaction studies: separation of the conformers of 2,3-dibromobuta-1,3-diene in the gas phase

“…No specific parameters were applied. The DFT results for the torsional potentials and dipole moments were in very good agreement with CCSD(T)-F12/ cc-pVTZ-F12, [42][43][44][45] calculations (Table 1). We additionally checked if including Douglas-Kroll-Hess (DKH) scalar relativistic effects on the DFT calculations would effect the results.…”

Glycolic Acid as a Vibrational Anharmonicity Benchmark

“…The extent of filling in these symbols represents increasing basis set completeness along the guiding lines (aVDZ, □; aVTZ, ◩; and aVQZ, ■). For MP2 and CCSD­(T), the third value was computed using their explicitly correlated F12 counterpart , with a VTZ-F12 basis. The green cross-hair represents experimental values within experimental uncertainty (width of the crossing bars) for pairs of observables (two band centers in Figure and a band center vs a band splitting in Figure ).…”

Analysis of the Proton Transfer Bands in the Infrared Spectra of Linear N2H+···OC and N2D+···OC Complexes Using Electric Field-Driven Classical Trajectories

“…Our spectral analysis involved two steps: (i) standard MD simulations were carried out to generate infrared spectra and (ii) the most prominent spectral features were then assigned using the DMD method. ,− In the MD simulations, the interaction potential, forces, , dipole moment, and their derivatives (see below) were evaluated as needed at every time step, i.e., “on the fly”, as the trajectories were propagated. We utilized the velocity-Verlet scheme to integrate Hamilton’s equations of motion using a shell script that interfaces the MOLPRO program and a set of FORTRAN procedures.…”