Tentatively standardized symmetry coordinates for vibrations of polyatomic molecules

Hypersilylphosphanylidene: A Facile Low‐Temperature Generation and Formation of Bis(hypersilyl)diphosphene and the Bis(hypersilyl)triphosphaallyl Anion

“…These calculations, known to spectroscopists as Wilson’s FG method,15 were performed using an enlarged version of the program ASYM40 16. ASYM40 needs the Hessian matrix and the atomic coordinates of the equilibrium geometry as input data as well as the symmetry coordinates, which were chosen according to standard methods described in the literature 17. Calculated PP, SiP and SiSi stretching force constants are summarised in Table 2.…”

“…[16] ASYM40 needs the Hessian matrix and the atomic coordinates of the equilibrium geometry as input data as well as the symmetry coordinates, which were chosen according to standard methods described in the literature. [17] Calculated PP, SiP and SiSi stretching force constants are summarised in [18] Furthermore, the calculations of the potential energy distributions (PED) show that ν(P=P) is indeed a group vibration in these diphosphenes, with f(PP) contributing as much as 86% to ν(P=P) in (H 3 Si) 3 SiP=PSi(SiH 3 ) 3 and 97% in (Me 3 Si) 3 SiP=PSi(SiMe 3 ) 3 . Coupling with other modes can be largely neglected.…”

“…[16] ASYM40 needs the Hessian matrix and the atomic coordinates of the equilibrium geometry as input data as well as the symmetry coordinates, which were chosen according to standard methods described in the literature. [17] Calculated PP, SiP and SiSi stretching force constants are summarised in Table 2. The P=P force constant is predicted as 326 and 332 N m -1 for (H 3 Si) 3 SiP=PSi-(SiH 3 ) 3 and (Me 3 Si) 3 SiP=PSi(SiMe 3 ) 3 , respectively.…”

Infrared spectrum of LiNaF2

“…A normal coordinate analysis for these types of molecules, assuming D2h symmetry, has been given elsewhere. 7 The space coordinates were chosen so that the z and y axes were in the plane of the molecules as in LiNaF2 shown in Figure 5. The 7Li2F2, 6Li2F2 and Na2F2 molecules were analyzed in a similar way to that described above for LiNaF2.…”

Carbon-13 Chemical Shift Tensors in Polycyclic Aromatic Compounds. 6.1 Single-Crystal Study of Perylene

“…Further, the shift derivative at the equilibrium position for angular harmonic motions is zero and for such vibrations only higher even order harmonic corrections contribute to the averaging. These contributions may be significant especially in the out-of-plane hydrogen harmonic vibrations, which on average are as large as 7° for naphthalene …”