dorsal/arxiv
View SchemaOCS in small para-hydrogen clusters: energetics and structure with N=1-8 complexed hydrogen molecules
| Authors | F. Paesani, R. E. Zillich, K. B. Whaley |
|---|---|
| Categories | |
| ArXiv ID | physics/0309074 |
| URL | https://arxiv.org/abs/physics/0309074 |
| DOI | 10.1063/1.1624058 |
Abstract
We determine the structure and energetics of complexes of the linear OCS molecule with small numbers of para-hydrogen molecules, N=1-8, using zero temperature quantum Monte Carlo methods. Ground state calculations are carried out with importance-sampled rigid body diffusion Monte Carlo (IS-RBDMC) and excited state calculations with the projection operator imaginary time spectral evolution (POITSE) methodology. The ground states are found to be highly structured, with a gradual build up of two axial rings as N increases to 8. Analysis of the azimuthal density correlations around the OCS molecule shows that these rings are quite delocalized for small N values, but become strongly localized for N \geq 5 . Excited state calculations are made for a range of total cluster angular momentum values and the rotational energy levels fitted to obtain effective rotational and distortion constants of the complexed OCS molecule as a function of cluster size N. Detailed analysis of these spectroscopic constants indicates that the complexes of OCS with para-hydrogen have an unusually rich variation in dynamical behavior, with sizes N=1-2 showing near rigid behavior, sizes N=3-4 showing extremely floppy behavior, and the larger sizes N=5-8 showing more rigid behavior again. The large values of the distortion constant D obtained for N=3-4 are rationalized in terms of the coupling between the OCS rotations and the "breathing" mode of the first, partially filled ring of para-hydrogen molecules.
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"abstract": "We determine the structure and energetics of complexes of the linear OCS\nmolecule with small numbers of para-hydrogen molecules, N=1-8, using zero\ntemperature quantum Monte Carlo methods. Ground state calculations are carried\nout with importance-sampled rigid body diffusion Monte Carlo (IS-RBDMC) and\nexcited state calculations with the projection operator imaginary time spectral\nevolution (POITSE) methodology. The ground states are found to be highly\nstructured, with a gradual build up of two axial rings as N increases to 8.\nAnalysis of the azimuthal density correlations around the OCS molecule shows\nthat these rings are quite delocalized for small N values, but become strongly\nlocalized for N \\geq 5 . Excited state calculations are made for a range of\ntotal cluster angular momentum values and the rotational energy levels fitted\nto obtain effective rotational and distortion constants of the complexed OCS\nmolecule as a function of cluster size N. Detailed analysis of these\nspectroscopic constants indicates that the complexes of OCS with para-hydrogen\nhave an unusually rich variation in dynamical behavior, with sizes N=1-2\nshowing near rigid behavior, sizes N=3-4 showing extremely floppy behavior, and\nthe larger sizes N=5-8 showing more rigid behavior again. The large values of\nthe distortion constant D obtained for N=3-4 are rationalized in terms of the\ncoupling between the OCS rotations and the \"breathing\" mode of the first,\npartially filled ring of para-hydrogen molecules.",
"arxiv_id": "physics/0309074",
"authors": [
"F. Paesani",
"R. E. Zillich",
"K. B. Whaley"
],
"categories": [
"physics.atm-clus"
],
"doi": "10.1063/1.1624058",
"title": "OCS in small para-hydrogen clusters: energetics and structure with N=1-8 complexed hydrogen molecules",
"url": "https://arxiv.org/abs/physics/0309074"
},
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