Quantum calculation of inelastic neutron scattering spectra of a hydrogen molecule inside a nanoscale cavity based on rigorous treatment of the coupled translation-rotation dynamics

We present a quantum methodology for the calculation of the inelastic neutron scattering (INS) spectra of an ${\mathrm{H}}_{2}$ molecule confined in a nanoscale cavity. Our approach incorporates the coupled five-dimensional translation-rotation (TR) energy levels and wave functions of the guest molecule. The computed INS spectra are highly realistic and reflect in full the complexity of the coupled TR dynamics on the anisotropic potential energy surfaces of the confining environment. Utilizing this methodology, we simulate the INS spectra of $p$- and $o$-H${}_{2}$ in the small cage of the structure II clathrate hydrate and compare them with the experimental data

Clusters containing open-shell molecules. III. Quantum five-dimensional/two-surface bound-state calculations on ArnOH van der Waals clusters (X2Π, n=4 to 12)

This paper presents a theoretical study of the bound states of the open-shell OH radical in its ground electronic state(X2Π) interacting with n Ar atoms, for n from 4 to 12. After freezing the geometry of the Arn cage or subunit at the equilibrium structure (preceding paper), we carry out nonadiabatic five-dimensional quantum dynamics calculations on two coupled potential energy surfaces, using an extension of the method previously applied to closed-shell ArnHFclusters [J. Chem. Phys. 103, 1829 (1995)]. The method is based on a discrete variable representation (DVR) for the translational motion of OH relative to Arn, combined with a finite basis representation of the OH hindered rotation and electronic structure, including spin–orbit effects. The pattern of OH hindered rotor levels in clusters is similar to that in Ar–OH itself, though extended over three to four times the energy range for n=4 to 9. Ar12OH has a nearly spherical shell of Ar atoms around the OH, so the anisotropic splitting is very small. For n=10 and 11, the anisotropy may be viewed as arising from holes in an otherwise spherical shell, and the resulting patterns of hindered rotor levels are inverted versions of those for Ar2OH and Ar–OH

H2, HD, and D2 inside C60: Coupled translation-rotation eigenstates of the endohedral molecules from quantum five-dimensional calculations

We have performed rigorous quantum five-dimensional (5D) calculations of the translation-rotation (T-R) energy levels and wave functions of H2, HD, and D2 inside C60. This work is an extension of our earlier investigation of the quantum T-R dynamics of H2@C60 [M. Xu et al., J. Chem. Phys. 128, 011101 (2008)] and uses the same computational methodology. Two 5D intermolecular potential energy surfaces (PESs) were employed, differing considerably in their well depths and the degree of confinement of the hydrogen molecule. Our calculations revealed pronounced sensitivity of the endohedral T-R dynamics to the differences in the interaction potentials, and to the large variations in the masses and the rotational constants of H2, HD, and D2. The T-R levels vary significantly in their energies and ordering on the two PESs, as well as from one isotopomer to another. Nevertheless, they all display the same distinctive patterns of degeneracies, which can be qualitatively understood and assigned in terms the model which combines the isotropic three-dimensional harmonic oscillator, the rigid rotor, and the coupling between the orbital and the rotational angular momenta of H2/HD/D2. The quantum number j associated with the rotation of H2, HD, and D2 was found to be a good quantum number for H2 and D2 on both PESs, while most of the T-R levels of HD exhibit strong mixing of two or more rotational basis functions with different j values

Risk identification in landslide monitoring

Monitoring klizišta ima značajnu ulogu u razumijevanju procesa klizanja, što je naročito važno u urbanim sredinama gdje aktiviranje klizišta može posredno ili neposredno ugroziti živote ljudi i nanijeti materijalne štete. U radu se identificiraju potencijalni izvori rizika pri monitoringu klizišta, te se objašnjavaju pojmovi svrhe mjerenja, mjernih veličina, mjerne opreme i rezultata mjerenja. Na primjeru dobro dokumentiranog klizišta Grmoščica u Zagrebu prikazat će se uloga monitoringa klizišta u urbanim sredinama.Landslide monitoring has an important role in the understanding of the landslide process, which is especially important in urban areas where landslide activation may directly or indirectly endanger human lives and cause material damage. Potential risk sources in landslide monitoring are identified in the paper, and terms measurement purpose, measurement parameters, measuring equipment and measurement results, are explained. The role of landslide monitoring in urban areas is presented using an example of well documented landslide Grmoščica in Zagreb

Quantum dynamics of coupled translational and rotational motions of H2 inside C60

We report rigorous quantum calculations of the translation-rotation (T-R) eigenstates of the H_2 molecule in C60. The resulting level structure can be explained in terms of a few dominant features. These include the coupling between the orbital and the rotational angular momenta of H_2 to give the total angular momentum λ, and the splitting of the sevenfold degeneracy of T-R levels with λ = 3 by the nonsphericity of C60, according to the rules of the icosahedral I_h group

Coupled translation-rotation eigenstates of H2 in C60 and C70 on the spectroscopically optimized interaction potential: Effects of cage anisotropy on the energy level structure and assignments

We have developed a quantitatively accurate pairwise additive five-dimensional (5D) potential energy surface (PES) for H2 in C60 through fitting to the recently published infrared (IR) spectroscopic measurements of this system for H2 in the vibrationally excited ν = 1 state. The PES is based on the three-site H2-C pair potential introduced in this work, which in addition to the usual Lennard-Jones (LJ) interaction sites on each H atom of H2 has the third LJ interaction site located at the midpoint of the H-H bond. For the optimal values of the three adjustable parameters of the potential model, the fully coupled quantum 5D calculations on this additive PES reproduce the six translation-rotation (T-R) energy levels observed so far in the IR spectra of H2@C60 to within 0.6%. This is due in large part to the greatly improved description of the angular anisotropy of the H2-fullerene interaction afforded by the three-site H2-C pair potential. The same H2-C pair potential spectroscopically optimized for H2@C60 was also used to construct the pairwise additive 5D PES of H2 (v = 1) in C70. This PES, because of the lower symmetry of C70 (D5h) relative to that of C60 (Ih), exhibits pronounced anisotropy with respect to the direction of the translational motion of H2 away from the cage center, unlike that of H2 in C60. As a result, the T-R energy level structure of H2 in C70 from the quantum 5D calculations on the optimized PES, the quantum numbers required for its assignment, and the degeneracy patterns which arise from the T-R coupling for translationally excited H2 are all qualitatively different from those determined previously for H2@C60 [M. Xu et al., J. Chem. Phys. 128, 011101 (2008)]

The Endofullerene HF@C 60 : Inelastic Neutron Scattering Spectra from Quantum Simulations and Experiment, Validity of the Selection Rule and Symmetry Breaking

Accurate quantum simulations of the low-temperature inelastic neutron scattering (INS) spectra of HF@C60 are reported for two incident neutron wavelengths. They are distinguished by the rigorous inclusion of symmetry-breaking effects in the treatment and having the spectra computed with HF as the guest, rather than H2 or HD, as in the past work. The results demonstrate that the precedent-setting INS selection rule, originally derived for H2 and HD in near-spherical nanocavities, applies also to HF@C60, despite the large mass asymmetry of HF and the strongly mixed character of its translation–rotation eigenstates. This lends crucial support to the theoretical prediction made earlier that the INS selection rule is valid for any diatomic molecule in near-spherical nanoconfinement. The selection rule remains valid in the presence of symmetry breaking but is modified slightly in an interesting way. Comparison is made with the recently published experimental INS spectrum of HF@C60. The agreement is very good, apart from one peak for which our calculations suggest a reassignment. This reassignment is consistent with the measured INS spectrum presented in this work, which covers an extended energy range

H2, HD, and D2 in the small cage of structure II clathrate hydrate: vibrational frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates

We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) vibrational state of H2, along with two isotopologues, providing a direct computation of vibrational frequency shifts. We show that obtaining a converged v = 1 vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermolecular degrees of freedom is needed to accurately describe the vibrational averaging over the delocalized wave function of the quantum ground state of the system. For the caged H2, our computed fundamental translational excitations, rotational j = 0 → 1 transitions, and frequency shifts of the stretch fundamental are in excellent agreement with recent quantum 5D (rigid H2) results [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)]. Our computed frequency shift of −43 cm−1 for H2 is only 14% away from the experimental value at 20 K