Electric properties of formaldehyde, thioformaldehyde, urea, formamide, and thioformamide—Post‐HF and DFT study

Abstract

Dipole moments , static electric polarizabilities ␣, and hyperpolarizabilities ␤ of formaldehyde, thioformaldehyde, urea, formamide, and thioformamide have been evaluated in the DFT and post-HF approximations. Within the DFT, the family of HCTH and hybrid functionals (B3LYP, B97-1) have been adopted. The qualitative and quantitative performance of both functional types have been examined by confrontation with the CCSD(T) method. The DFT model appears to be adequate for dipole moments and polarizabilities, while the hyperpolarizabilities are exaggerated, especially ␤ yyy (too negative) and ␤ zzz (too positive) components. The replacement of oxygen by sulfur reduces the DFT hyperpolarizability, which contradicts an increase predicted with the post-HF approach. HCTH dipole moments in majority of cases are in better agreement with the CCSD(T) estimates than are the hybrid functionals. On the other hand, the hybrid functionals perform slightly better for polarizability and hyperpolarizability evaluations. The effects of basis set size with augcc-pVXZ (X ϭ D, T, Q) on the electric properties have also been studied. The sensitivity of the electric properties to the basis set effects increases from the dipole moment to the hyperpolarizability. The axial ␣ zz and ␤ zzz components display smaller sensitivity to the basis set extension. The carbonyl/thiocarbonyl containing molecules are characterized by negative/positive sign of hyperpolarizability vector projection into the dipole moment direction.

Low-energy electron collisions with formamide using theR-matrix method

“…Meanwhile, the dipole moments calculated with the other methods are also larger than the experimental result, for example, 1.540, 1.577, and 1.554 a.u. predicted with MP2, CCSD, and CCSD(T) methods, respectively [40]. In our scattering calculations, three scattering models are examined.…”

Optimal control of the orientation and alignment of an asymmetric-top molecule with terahertz and laser pulses

“…In this molecule, as the dipole moment lies along the molecule-fixed z axis and the largest component of the polarizability tensor is α zz (using the I r representation), the orientation and alignment will be qualitatively different. 43 In the case of C s or C 1 symmetry molecules, the theoretical treatment should be modified to account for the fact that a block diagonalization of the operators involved in the calculation is not possible as the dipole moment is not parallel to either principal axes of inertia. Such would be the case for the C s symmetry vinyl chloride (H 2 CCHCl) molecule with a dipole moment neither parallel to the a nor to the b principal axes.…”

Mountaineering Strategy to Excited States: Highly Accurate Oscillator Strengths and Dipole Moments of Small Molecules

“…A very accurate measurement of 𝜇 GS for formaldehyde is available at 2.3321±0.0005 D (molecular beam electric resonance spectroscopy), 159 and our theoretical TBE of 2.41±0.01 D seems slightly too large, but is in very good agreement with previous CCSD(T)/CBS (2.393 D) 47 and CCSD(T)/aug-cc-pVQZ (2.382 D) estimates. 166 As early as 2004, Hirata proposed a CCSDT/aug-cc-pVDZ value of 𝜇 GS at 2.33 D, 74 right on the experimental spot, but an experimental geometry was used and the orbital relaxation effects neglected, which might have induced a very slight error compensation. For the hallmark lowest 𝑛 → 𝜋 ★ transition, one can find several experimental estimates of 𝜇 ES : 1.48±0.07, 172 1.56±0.07, 173 1.4±0.1 D, 174 1.53±0.11D, 160 and 1.47 D. 164 Somehow surprisingly, the most recent value obtained by Stark quantum beat spectroscopy has hardly been considered as reference in theoretical works than the maximal measured value of 1.56 D. On the theory side, one can highlight two significant earlier contributions (on the ES geometry): 1.48 D (CCSDT/aug-cc-pVDZ) 74 and 1.73 D (CC2/aug-cc-pVQZ).…”