Description of C(sp²)−C(sp²) Rotation in Butadiene by Density Functionals

Abstract

The torsional potential of 1,3-butadiene has been calculated using several ab initio methodologies. For each value of the CdC-CdC torsional angle, the fully relaxed geometry and energy have been determined using the Hartree-Fock (HF) method, Mo ¨eller-Plesset perturbation theory up to the second order (MP2), and the coupled-cluster method with single, doubles, and parethentical triples (CCSD(T)), as well as using several exchange-correlation combinations of functionals in density functional theory (DFT) calculations. From the results obtained, the achievements and drawbacks of current density functionals in the description of torsional profiles have been rationalized, and some possible breakthroughs have been proposed to improve their performance.

Double-hybrid density functionals: merging wavefunction and density approaches to get the best of both worlds

“…Successful applications of these composite methods have been reported repeatedly in the literature [49][50][51]. If we assume enough similarities between one-electron orbitals arising from separate solutions of the Hartree-Fock or Kohn-Sham self-consistent equations [52], and then we neglect every kinetic or potential energy differences between corresponding one-particle mean values, the MC-based exchange-correlation energy might be expressed as: (27) as a function of the following weights (w i ),…”

“…As a matter of illustration, a variant of canonical MP2, that scales differently the contribution to correlation energy arising from same-or opposite-spin pairs, was recently introduced (the Spin-Component-Scaled MP2 [70])to largely remedy the intrinsic deficiencies of the original MP2 method. Actually, commonly used correlation functionals mainly introduce short-range dynamical correlation effects [71,72], and thus partly neglect correlations (i.e., left-right) between parallel-spin pairs, which leaves this responsibility to the MP2-type term of double-hybrid functionals. Therefore, due to this unbalanced treatment of correlation effects, some recent expressions (e.g.…”

“…As a matter of illustration, the energy barrier for the auto-isomerization of cyclobutadiene is known to be a longstanding problem [151][152][153][154]. The interconversion between two iso-energetic (rectangular) forms passes through a (square) transition state having degenerate frontier orbitals, see Figure 5, which would thus need a multiconfigurational treatment or a more generalised treatment than that provided by current methods [155][156][157]. Actually, the results provided by B2-PLYP (PBE0-DH), with the def2-QZVP basis set, severely overestimate that energy barrier: 23.5 (25.2) kcal/mol, respectively, to be compared against sophisticated multiconfigurational MR-BWCCSD(T) results (7.0 kcal/mol, taken from Ref.…”

Density functional theory study on electron and hole transport properties of organic pentacene derivatives with electron‐withdrawing substituent

“…[3,8,15] More and more technical and academic studies of organic semiconductor materials have been carried out to develop high mobility electronic devices. [16][17][18][19] Bao and his coworkers have fabricated the high-performance single-crystal field-effect transistors with the synthesized organic semiconductors [1,2,20] and Shuai and his coworkers have systematically developed the theoretical models to simulate the charge transport in the organic conjugated systems. [21][22][23] However, due to a lack of stable molecular materials with strong electron injection and considerable electron mobility, investigations of n-type semiconductors have been limited compared with p-type ones.…”

Trends in molecular design strategies for ambient stable n-channel organic field effect transistors

“…Increasing the amount of HF-exchange decreases defect sizes, increases spincontamination, 119 122 and the direct coupling method. 123 The simplest of the three, the energy-splitting-in-dimer method, however, tends to underestimate t. 124 As mobilities increase with increasing t and decreasing l while both increase with HF-exchange, it is possible to manipulate the predicted mobilities by calculating l and t with different density functionals. 99 However, as the measured mobilities differ by orders of magnitude depending on the processing conditions, 39 forcing agreement between theory and experiment leads to little insight.…”