Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions

Pierloot, Kristine; Dumez, Birgit; Widmark, Per‐Olof; Roos, Bj�rn O.

doi:10.1007/bf01113842

Cited by 510 publications

(119 citation statements)

References 22 publications

Supporting

Mentioning

119

Contrasting

Order By: Relevance

“…The vertical excitation energies, the global minima of the ground and the π 3s Rydberg states, and the minimum energy conical intersections (MECI) between the π 3s Rydberg and ππ* valence states were optimized employing a 3s2p1d/2s1p atomic natural orbital (ANO) basis 34 set in conjunction with multi-reference configuration interaction with single and double excitations (MR-CISD) wavefunctions. The ANO basis was augmented with a pair of s and π diffuse functions, optimized from cationic energies and expanded in a basis of universal exponents, [35][36][37] centered at the ethylenic carbons of each molecule.…”

Section: B Computational Methodsmentioning

confidence: 99%

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

Boguslavskiy

Schalk

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

Excited state unimolecular reactions of some polyenes exhibit localization of their dynamics at a single ethylenic double bond. Here we present studies of the fundamental photophysical processes in the ethylene unit itself. Combined femtosecond time-resolved photoelectron spectroscopy (TR-PES) and ab initio quantum chemical calculations was applied to the study of excited state dynamics in cis-butene, trans-butene, trimethylethylene, and tetramethylethylene, following initial excitation to their respective π 3s Rydberg states. The wavelength dependence of the π 3s Rydberg state dynamics of tetramethylethylene was investigated in more detail. The π 3s Rydberg to ππ * valence state decay rate varies greatly with substituent: the 1,2-di-and tri-methyl substituted ethylenes (cis-butene, trans-butene, and trimethylethylene) show an ultrafast decay (∼20 fs), whereas the fully methylated tetramethylethylene shows a decay rate of 2 to 4 orders of magnitude slower. These observations are rationalized in terms of topographical trends in the relevant potential energy surfaces, as found from ab initio calculations: (1) the barrier between the π 3s state and the ππ* state increases with increasing methylation, and (2) the π 3s/ππ* minimum energy conical intersection displaces monotonically away from the π 3s Franck-Condon region with increasing methylation. The use of systematic methylation in combination with TRPES and ab initio computation is emerging as an important tool in discerning the excited state dynamics of unsaturated hydrocarbons.

show abstract

Section: B Computational Methodsmentioning

confidence: 99%

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

Boguslavskiy

Schalk

et al. 2011

The Journal of Chemical Physics

View full text Add to dashboard Cite

show abstract

“…The calculations used CZh symmetry and an ANO-S [14] one-particle basis set [C.ANO-S 3s2pld/H.ANO-S 2slpl. The selection of the active space is a crucial step in a CASSCF calculation.…”

Section: Computational Detailsmentioning

confidence: 99%

A theoretical study of the 2¹A_g← 1¹A_gtwo-photon transition and its vibronic band intrans-stilbene

et al. 2002

View full text Add to dashboard Cite

A g ← 1 1 A g two-photon transition and its vibronic band in trans-stilbene,The two-photon spectrum of the 2'A, t 1' A, transition in trans-stilbene has been calculated at the complete active space self-consistent field (CASSCF) level of theory. Energies were obtained at the complete active space second-order perturbation (CASPT2) level of theory, while the geometries of both the initial and final states were optimized at the CASSCF level. The energy and the geometry optimizations were performed using an active space of 14 electrons in 14 active R orbitals. The vibrational frequencies of both states and the two-photon transition (TPT) cross-section were calculated with a smaller active space where the two lowest T orbitals were kept inactive. A newly implemented algorithm, in the quantum chemical package Molcas was used to determine the two-photon transition intensity. This method requires only the linear response of the CASSCF wavefunction. Furthermore, the vibronic structure of this TPT was studied. The Franck-Condon factors were obtained by calculating the overlap between the vibrational states involved, which were determined from the force fields of both the initial and final states, at the CASSCF level of theory. The results are in agreement with experiment.

show abstract

“…41 In order to arrive at a satisfactory description of all excited states at the CASPT2 level (i.e., remove intruder states), it was necessary to resort to the level shifting technique, 42 whereby it was carefully assured that no artifacts are introduced. All CASSCF/CASPT2 calculations were carried out with the MOLCAS 4 suite of programs.…”

mentioning

confidence: 99%

Ground state multiplicity of acylnitrenes: computational and experimental studies

2005

View full text Add to dashboard Cite

The singlet-triplet energy splitting (∆E ST = E S -E T ) was calculated for formylnitrene (5) and for the syn and anti rotamers of carboxynitrene HOC(O)N (6) by the CCSD(T) method. Extrapolation of ∆E ST to a complete basis set was calculated to be negative for 5 and strongly positive for 6. Similar results were obtained by the G2 procedure. The reason for the dramatic stabilization of the singlet state appeared to be a special bonding interaction between the nitrogen and oxygen atoms, which results in the structure intermediate between those of nitrene and oxazirene. It was found that the B3LYP/6 31G(d) method overestimates ∆E ST by ~9 kcal mol -1 for 5 and by ~7 kcal mol -1 for 6. Taking into account this overestimation and the results of DFT calculations, it was concluded that benzoylnitrene has a singlet ground state. It was proved experimentally using photolysis of benzoyl azide in an argon matrix at 12 K that benzoylnitrene has a singlet ground state and its structure is similar to that of oxazirene. Nevertheless, these singlet intermediates have low barrier to the aziridine formation, which is traditionally considered to be a typical singlet nitrene reaction.Photolysis of carbonyl azides RC(O)N 3 gives rise to two types of products: (i) isocyanates RNCO (the prod ucts of the photo Curtius rearrangement 1 ) and (ii) bimo lecular trapping products typical of the reactions of sin glet carbonylnitrenes RC(O)N. 2 It has, however, been shown that the yield of isocyanates upon photolysis of a series of carbonyl azides (R = tert butyl, aryl) remains constant (~40 50%) irrespective of the presence or ab

show abstract

Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions

Cited by 510 publications

References 22 publications

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

A theoretical study of the 2¹A_g← 1¹A_gtwo-photon transition and its vibronic band intrans-stilbene

Ground state multiplicity of acylnitrenes: computational and experimental studies

Contact Info

Product

Resources

About

Density matrix averaged atomic natural orbital (ANO) basis sets for correlated molecular wave functions

Cited by 510 publications

References 22 publications

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

Ultrafast non-adiabatic dynamics of methyl substituted ethylenes: The π3s Rydberg state

A theoretical study of the 21Ag← 11Agtwo-photon transition and its vibronic band intrans-stilbene

Ground state multiplicity of acylnitrenes: computational and experimental studies

Contact Info

Product

Resources

About

A theoretical study of the 2¹A_g← 1¹A_gtwo-photon transition and its vibronic band intrans-stilbene