Pub Date : 2007-10-15DOI: 10.1142/S021830130800963X
M. Brack, P. Winkler, M. Murthy
We first give a short review of the ``local-current approximation'' (LCA), derived from a general variation principle, which serves as a semiclassical description of strongly collective excitations in finite fermion systems starting from their quantum-mechanical mean-field ground state. We illustrate it for the example of coupled translational and compressional dipole excitations in metal clusters. We then discuss collective electronic dipole excitations in C$_{60}$ molecules (Buckminster fullerenes). We show that the coupling of the pure translational mode (``surface plasmon'') with compressional volume modes in the semiclasscial LCA yields semi-quantitative agreement with microscopic time-dependent density functional (TDLDA) calculations, while both theories yield qualitative agreement with the recent experimental observation of a ``volume plasmon''.
{"title":"Coupling of Surface and Volume Dipole Oscillations in C-60 Molecules","authors":"M. Brack, P. Winkler, M. Murthy","doi":"10.1142/S021830130800963X","DOIUrl":"https://doi.org/10.1142/S021830130800963X","url":null,"abstract":"We first give a short review of the ``local-current approximation'' (LCA), derived from a general variation principle, which serves as a semiclassical description of strongly collective excitations in finite fermion systems starting from their quantum-mechanical mean-field ground state. We illustrate it for the example of coupled translational and compressional dipole excitations in metal clusters. We then discuss collective electronic dipole excitations in C$_{60}$ molecules (Buckminster fullerenes). We show that the coupling of the pure translational mode (``surface plasmon'') with compressional volume modes in the semiclasscial LCA yields semi-quantitative agreement with microscopic time-dependent density functional (TDLDA) calculations, while both theories yield qualitative agreement with the recent experimental observation of a ``volume plasmon''.","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2007-10-15","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"131937712","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
{"title":"PRACTICABLE FACTORIZED TDLDA FOR ARBITRARY DENSITY- AND CURRENT-DEPENDENT FUNCTIONALS","authors":"V. Nesterenko, J. Kvasil, P. Reinhard","doi":"10.1007/1-4020-4528-X_5","DOIUrl":"https://doi.org/10.1007/1-4020-4528-X_5","url":null,"abstract":"","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"14 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2005-12-07","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124346053","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We performed bound state calculations to obtain the first few vibrational states for the Ar3 molecular system. The equations used are of Faddeev‐type and are solved directly as three‐dimensional equations in configuration space, i.e. without resorting to an explicit partial wave decomposition. In addition to realistic pairwise interactions, we employ long range three‐body forces. Our results are in good agreement with those obtained by other methods based on partial wave expansion and show a significant contribution of the three‐body forces (>10%) to the binding energy and thus their inclusion is, in general, warranted in studying similar triatomic systems.
{"title":"Triatomic molecular systems and three‐body forces: the Ar3 case","authors":"M. Lekala, S. Sofianos","doi":"10.1063/1.1932952","DOIUrl":"https://doi.org/10.1063/1.1932952","url":null,"abstract":"We performed bound state calculations to obtain the first few vibrational states for the Ar3 molecular system. The equations used are of Faddeev‐type and are solved directly as three‐dimensional equations in configuration space, i.e. without resorting to an explicit partial wave decomposition. In addition to realistic pairwise interactions, we employ long range three‐body forces. Our results are in good agreement with those obtained by other methods based on partial wave expansion and show a significant contribution of the three‐body forces (>10%) to the binding energy and thus their inclusion is, in general, warranted in studying similar triatomic systems.","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"6 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2004-10-05","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"124240688","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Pub Date : 2001-12-10DOI: 10.1142/9789812702876_0021
M. Payami
Using the stabilized jellium model with self-compression, we have calculated the dissociation energies and the barrier heights for the binary fragmentation of charged silver clusters. At each step of calculations, we have used the relaxed-state sizes and energies of the clusters. The results for the doubly charged Ag clusters predict a critical size, at which evaporation dominates the fission, in good agreement with the experiment. Comparing the dissociation energies and the fission barrier heights with the experimental ones, we conclude that in the experiments the fragmentation occurs before the full structural relaxation expected after the ionization of the cluster. In the decays of Ag$_N^{4+}$ clusters, the results predict that the charge-symmetric fission processes are dominant for smaller clusters, and the charge-asymmetric fission processes become dominant for sufficiently larger clusters.
{"title":"Fragmentation of positively charged metal clusters in stabilized jellium model with self-compression","authors":"M. Payami","doi":"10.1142/9789812702876_0021","DOIUrl":"https://doi.org/10.1142/9789812702876_0021","url":null,"abstract":"Using the stabilized jellium model with self-compression, we have calculated the dissociation energies and the barrier heights for the binary fragmentation of charged silver clusters. At each step of calculations, we have used the relaxed-state sizes and energies of the clusters. The results for the doubly charged Ag clusters predict a critical size, at which evaporation dominates the fission, in good agreement with the experiment. Comparing the dissociation energies and the fission barrier heights with the experimental ones, we conclude that in the experiments the fragmentation occurs before the full structural relaxation expected after the ionization of the cluster. In the decays of Ag$_N^{4+}$ clusters, the results predict that the charge-symmetric fission processes are dominant for smaller clusters, and the charge-asymmetric fission processes become dominant for sufficiently larger clusters.","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"8 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"2001-12-10","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"122187335","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
Recent far-infrared vibration-rotation tunneling (FIR-VRT) experiments pose new challenges to theory because the interpretation and prediction of such spectra requires a detailed understanding of the potential energy surface (PES) away from minima. In particular we need a global description of the PES in terms of a complete reaction graph. Hence all the transition states and associated mechanisms which might give rise to observable tunneling splittings must be characterized. It may be possible to guess the detailed permutations of atoms from the transition state alone, but experience suggests this is unwise. In this contribution a brief overview of the issues involved in treating the large amplitude motions of such systems will be given, with references to more detailed discussions and some specific examples. In particular we will consider the effective molecular symmetry group, the classification of rearrangement mechanisms, the location of minima and transition states and the calculation of reaction pathways. The application of these theories to small water clusters ranging from water dimer to water hexamer will then be considered. More details can be found in recent reviews.
{"title":"REARRANGEMENTS AND TUNNELING SPLITTINGS IN SMALL WATER CLUSTERS","authors":"D. Wales","doi":"10.1063/1.480183","DOIUrl":"https://doi.org/10.1063/1.480183","url":null,"abstract":"Recent far-infrared vibration-rotation tunneling (FIR-VRT) experiments pose new challenges to theory because the interpretation and prediction of such spectra requires a detailed understanding of the potential energy surface (PES) away from minima. In particular we need a global description of the PES in terms of a complete reaction graph. Hence all the transition states and associated mechanisms which might give rise to observable tunneling splittings must be characterized. It may be possible to guess the detailed permutations of atoms from the transition state alone, but experience suggests this is unwise. \u0000In this contribution a brief overview of the issues involved in treating the large amplitude motions of such systems will be given, with references to more detailed discussions and some specific examples. In particular we will consider the effective molecular symmetry group, the classification of rearrangement mechanisms, the location of minima and transition states and the calculation of reaction pathways. The application of these theories to small water clusters ranging from water dimer to water hexamer will then be considered. More details can be found in recent reviews.","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"27 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1998-10-16","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"121381112","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
We discuss the calculation of collective excitations in atomic clusters using the time-dependent local density approximation. In principle there are many formulations of the TDLDA, but we have found that a particularly efficient method for large clusters is to use a coordinate space mesh and the algorithms for the operators and the evolution equations that had been developed for the nuclear time-dependent Hartree-Fock theory. The TDLDA works remarkably well to describe the strong excitations in alkali metal clusters and in carbon clusters. We show as an example the benzene molecule, which has two strong features in its spectrum. The systematics of the linear carbon chains is well reproduced, and may be understood in rather simple terms.
{"title":"The time-dependent local density approximation for collective excitations of atomic clusters","authors":"G. Bertsch, K. Yabana","doi":"10.1063/1.54541","DOIUrl":"https://doi.org/10.1063/1.54541","url":null,"abstract":"We discuss the calculation of collective excitations in atomic clusters using the time-dependent local density approximation. In principle there are many formulations of the TDLDA, but we have found that a particularly efficient method for large clusters is to use a coordinate space mesh and the algorithms for the operators and the evolution equations that had been developed for the nuclear time-dependent Hartree-Fock theory. The TDLDA works remarkably well to describe the strong excitations in alkali metal clusters and in carbon clusters. We show as an example the benzene molecule, which has two strong features in its spectrum. The systematics of the linear carbon chains is well reproduced, and may be understood in rather simple terms.","PeriodicalId":296915,"journal":{"name":"arXiv: Atomic and Molecular Clusters","volume":"73 1","pages":"0"},"PeriodicalIF":0.0,"publicationDate":"1997-06-27","publicationTypes":"Journal Article","fieldsOfStudy":null,"isOpenAccess":false,"openAccessPdf":"","citationCount":null,"resultStr":null,"platform":"Semanticscholar","paperid":"115301646","PeriodicalName":null,"FirstCategoryId":null,"ListUrlMain":null,"RegionNum":0,"RegionCategory":"","ArticlePicture":[],"TitleCN":null,"AbstractTextCN":null,"PMCID":"","EPubDate":null,"PubModel":null,"JCR":null,"JCRName":null,"Score":null,"Total":0}
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