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Shiro Koseki - One of the best experts on this subject based on the ideXlab platform.
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multiconfiguration self consistent field study on formonitrile imine and n substituted nitrile imines hcn2 r Energy Component analysis of the pseudo jahn teller effect
Journal of Physical Chemistry A, 2017Co-Authors: Azumao Toyota, Takashi Muramatsu, Shiro KosekiAbstract:Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN2–R (R = Li, BeH, BH2, CH3, CN, CCH, C6H5, NH2, OH, and F) (2–11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn–Teller (JT) distortion from a linear C∞v structure to a C1 structure via a planar bent Cs structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent Cs structure for 2, 3, and 7 and to a C1 structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1–11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, Energy Component analyses were carried out at the MCSC...
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Energy Component Analysis of the Pseudo‐Jahn‐Teller Effect in the Bicyclic Nonalternant Hydrocarbons: The Pentalenoid and Heptalenoid Systems
ChemInform, 2010Co-Authors: Azumao Toyota, Shiro KosekiAbstract:To gain insight into the nature of the pseudo-Jahn−Teller (JT) effect, an Energy Component analysis has been carried out for the bicyclic nonalternant hydrocarbons termed pentalenoid and heptalenoid systems by using the ab initio RHF method with 6-31G(d) basis set. Inspection of the Energy Component comprised in the total Energy reveals that the stability of a less symmetrical nuclear configuration is largely responsible for the decrease in the internuclear repulsion Energy and the interelectronic repulsion Energy due to σ electrons. These observations are consistent with an expansion of the carbon skeleton brought about by the pseudo-JT distortion. Another Energy Component also plays an essential role in the pseudo-JT stabilization: For the examples, the preference for the C2h structure rather than the D2h one for the pentalene arises from a decrease in the interelectronic repulsion Energy due to π electrons, while that for heptalene results from a lowering of the nuclear−electron attraction Energy due ...
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Ab Initio MCSCF Study on Eight π-Electron Heterocyclic Conjugated Systems: Energy Component Analysis of the Pseudo-Jahn−Teller Distortion from Planarity
The Journal of Physical Chemistry A, 2001Co-Authors: Azumao Toyota, Masahiro Shiota, Yukihiko Nagae, Shiro KosekiAbstract:To clarify the origin of nonplanarity in eight π-electron heterocyclic conjugated systems, an Energy Component analysis was carried out for the ground states by using ab initio MCSCF method with 6-...
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Energy Component Analysis of the Pseudo-Jahn-Teller Effect in the Ground State of the Triafulvalene Anion, Pentafulvalene Cation, and Heptafulvalene Anion Radicals
The Journal of Physical Chemistry A, 1998Co-Authors: Azumao Toyota, Shiro KosekiAbstract:To understand the nature of the pseudo-Jahn−Teller (JT) effect, an Energy Component analysis of the total Energy was carried out in the ground state of the titled ion radicals by using the MCSCF me...
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Ab Initio MCSCF Study on Electronically Excited Singlet States of Fulvalene Systems: Energy Component Analysis of the Pseudo-Jahn−Teller Effect
The Journal of Physical Chemistry A, 1998Co-Authors: Azumao Toyota, Shiro KosekiAbstract:Geometry optimizations of the lowest (second) excited singlet states of the fulvalene systems were carried out by using the ab initio MCSCF method with the 6-31G(d) basis set. The electronically excited molecules are found to undergo a pseudo-Jahn−Teller (JT) distortion from D2h to C2v. On the basis of the results obtained, an Energy Component analysis of the total Energy has been carried out to elucidate the physical picture of the pseudo-JT effect. Inspection of the Energy Components comprised in the total Energy reveals that the stability of a less symmetric structure (C2v) is attributable commonly to the Energy lowerings of the internuclear repulsion term and the interelectronic repulsive and kinetic terms due to σ electrons. These observations are consistent with an expansion of the carbon skeleton brought about by the pseudo-JT bond distortion. It is further found that in triafulvalene and heptafulvalene the nuclear−electron attractive and interelectronic repulsive terms due to π electrons contribut...
Azumao Toyota - One of the best experts on this subject based on the ideXlab platform.
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multiconfiguration self consistent field study on formonitrile imine and n substituted nitrile imines hcn2 r Energy Component analysis of the pseudo jahn teller effect
Journal of Physical Chemistry A, 2017Co-Authors: Azumao Toyota, Takashi Muramatsu, Shiro KosekiAbstract:Stable geometrical structures for formonitrile imine (1) and N-substituted nitrile imines HCN2–R (R = Li, BeH, BH2, CH3, CN, CCH, C6H5, NH2, OH, and F) (2–11) were examined by using the multiconfiguration self-consistent-field (MCSCF) method followed by second-order configuration interaction (SOCI) calculations and second-order multiconfiguration quasi-degenerate perturbation theory (MCQDPT2) calculations, together with the aug-cc-pVTZ basis sets. The results show that 1 suffers a pseudo-Jahn–Teller (JT) distortion from a linear C∞v structure to a C1 structure via a planar bent Cs structure. Each of the others is found to undergo pseudo-JT distortion from a symmetrical structure to a planar bent Cs structure for 2, 3, and 7 and to a C1 structure for 4, 5, 6, 8, 9, 10, and 11. At the stationary structures of 1–11, the structural characteristics were briefly discussed in terms of allenic and propargylic. To elucidate the nature of pseudo-JT distortions, Energy Component analyses were carried out at the MCSC...
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Energy Component Analysis of the Pseudo‐Jahn‐Teller Effect in the Bicyclic Nonalternant Hydrocarbons: The Pentalenoid and Heptalenoid Systems
ChemInform, 2010Co-Authors: Azumao Toyota, Shiro KosekiAbstract:To gain insight into the nature of the pseudo-Jahn−Teller (JT) effect, an Energy Component analysis has been carried out for the bicyclic nonalternant hydrocarbons termed pentalenoid and heptalenoid systems by using the ab initio RHF method with 6-31G(d) basis set. Inspection of the Energy Component comprised in the total Energy reveals that the stability of a less symmetrical nuclear configuration is largely responsible for the decrease in the internuclear repulsion Energy and the interelectronic repulsion Energy due to σ electrons. These observations are consistent with an expansion of the carbon skeleton brought about by the pseudo-JT distortion. Another Energy Component also plays an essential role in the pseudo-JT stabilization: For the examples, the preference for the C2h structure rather than the D2h one for the pentalene arises from a decrease in the interelectronic repulsion Energy due to π electrons, while that for heptalene results from a lowering of the nuclear−electron attraction Energy due ...
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Ab Initio MCSCF Study on Eight π-Electron Heterocyclic Conjugated Systems: Energy Component Analysis of the Pseudo-Jahn−Teller Distortion from Planarity
The Journal of Physical Chemistry A, 2001Co-Authors: Azumao Toyota, Masahiro Shiota, Yukihiko Nagae, Shiro KosekiAbstract:To clarify the origin of nonplanarity in eight π-electron heterocyclic conjugated systems, an Energy Component analysis was carried out for the ground states by using ab initio MCSCF method with 6-...
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Energy Component Analysis of the Pseudo-Jahn-Teller Effect in the Ground State of the Triafulvalene Anion, Pentafulvalene Cation, and Heptafulvalene Anion Radicals
The Journal of Physical Chemistry A, 1998Co-Authors: Azumao Toyota, Shiro KosekiAbstract:To understand the nature of the pseudo-Jahn−Teller (JT) effect, an Energy Component analysis of the total Energy was carried out in the ground state of the titled ion radicals by using the MCSCF me...
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Ab Initio MCSCF Study on Electronically Excited Singlet States of Fulvalene Systems: Energy Component Analysis of the Pseudo-Jahn−Teller Effect
The Journal of Physical Chemistry A, 1998Co-Authors: Azumao Toyota, Shiro KosekiAbstract:Geometry optimizations of the lowest (second) excited singlet states of the fulvalene systems were carried out by using the ab initio MCSCF method with the 6-31G(d) basis set. The electronically excited molecules are found to undergo a pseudo-Jahn−Teller (JT) distortion from D2h to C2v. On the basis of the results obtained, an Energy Component analysis of the total Energy has been carried out to elucidate the physical picture of the pseudo-JT effect. Inspection of the Energy Components comprised in the total Energy reveals that the stability of a less symmetric structure (C2v) is attributable commonly to the Energy lowerings of the internuclear repulsion term and the interelectronic repulsive and kinetic terms due to σ electrons. These observations are consistent with an expansion of the carbon skeleton brought about by the pseudo-JT bond distortion. It is further found that in triafulvalene and heptafulvalene the nuclear−electron attractive and interelectronic repulsive terms due to π electrons contribut...
John F. Kerridge - One of the best experts on this subject based on the ideXlab platform.
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long term compositional variation in solar corpuscular radiation evidence from nitrogen isotopes in the lunar regolith
Reviews of Geophysics, 1993Co-Authors: John F. KerridgeAbstract:Implantation of solar corpuscular radiation into the lunar surface generates a population of solar atoms in the rims of lunar regolith grains. Laboratory analysis of those atoms can yield a measure of solar composition. Nitrogen trapped in the lunar regolith consists of at least two Components, putatively originating in the Sun, differing in release temperature and therefore probably in implantation Energy. The higher-Energy Component is depleted in 15N relative to the lower-Energy Component by amounts that range up to at least 20%. These Components superficially resemble those identified previously in the solar-derived light noble gases, though with several marked differences. Thus the higher-Energy noble gas Components are depleted in the lighter isotope. Unlike the noble gas case, the 15N/14N ratios of both N Components vary with antiquity in a complex fashion; the lower-Energy Component echoes the variations in the higher-Energy Component which dominate the isotopic evolution of the bulk samples. The magnitude of the bulk sample variation exceeds 30%; the higher-Energy Component varies by at least 25%. The bulk long-term trend in 15N/14N does not result from variations in mixing ratio of the two Components. Both the compositional difference between the Components and the long-term variations within them apparently originate in the Sun, though this conclusion is inconsistent with current understanding of solar structure and evolution. The nitrogen isotopic record therefore appears to represent a major challenge to solar physics.
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Long‐term compositional variation in solar corpuscular radiation: Evidence from nitrogen isotopes in the lunar regolith
Reviews of Geophysics, 1993Co-Authors: John F. KerridgeAbstract:Implantation of solar corpuscular radiation into the lunar surface generates a population of solar atoms in the rims of lunar regolith grains. Laboratory analysis of those atoms can yield a measure of solar composition. Nitrogen trapped in the lunar regolith consists of at least two Components, putatively originating in the Sun, differing in release temperature and therefore probably in implantation Energy. The higher-Energy Component is depleted in 15N relative to the lower-Energy Component by amounts that range up to at least 20%. These Components superficially resemble those identified previously in the solar-derived light noble gases, though with several marked differences. Thus the higher-Energy noble gas Components are depleted in the lighter isotope. Unlike the noble gas case, the 15N/14N ratios of both N Components vary with antiquity in a complex fashion; the lower-Energy Component echoes the variations in the higher-Energy Component which dominate the isotopic evolution of the bulk samples. The magnitude of the bulk sample variation exceeds 30%; the higher-Energy Component varies by at least 25%. The bulk long-term trend in 15N/14N does not result from variations in mixing ratio of the two Components. Both the compositional difference between the Components and the long-term variations within them apparently originate in the Sun, though this conclusion is inconsistent with current understanding of solar structure and evolution. The nitrogen isotopic record therefore appears to represent a major challenge to solar physics.
Paul J Steinhardt - One of the best experts on this subject based on the ideXlab platform.
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effects of the sound speed of quintessence on the microwave background and large scale structure
Physical Review D, 2003Co-Authors: Simon Dedeo, Robert R Caldwell, Paul J SteinhardtAbstract:One of the greatest challenges in cosmology today is to identify the nature of the dark Energy Component that comprises most of the Energy density of the universe and that is causing the expansion of the universe to accelerate.[1] Two candidates are a cosmological constant (or vacuum density) and quintessence,[2] a dynamical Energy Component with negative pressure. Distinguishing the two is important for cosmology in order to refine our knowledge of the composition of the universe and to trace more accurately its evolution. It is even more important for fundamental physics since it informs us how we must modify unified theories to incorporate dark Energy.
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cluster abundance constraints for cosmological models with a time varying spatially inhomogeneous Energy Component with negative pressure
The Astrophysical Journal, 1998Co-Authors: Limin Wang, Paul J SteinhardtAbstract:The abundance of rich clusters is a strong constraint on the mass power spectrum. The current constraint can be expressed in the form ? -->8 ?${γ}m$ -->=0.5?0.1, where ?8 is the rms mass fluctuation on 8 h-1 Mpc scales, ?m is the ratio of matter density to the critical density, and ? is model dependent. In this paper, we determine a general expression for ? that applies to any models with a mixture of cold dark matter plus cosmological constant or quintessence (a time-evolving, spatially inhomogeneous Component with negative pressure) including dependence on the spectral index n, the Hubble constant h, and the equation of state of the quintessence Component w. The cluster constraint is combined with COBE measurements to identify a range of best-fitting models. The constraint from the evolution of rich clusters is also discussed.
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cosmological imprint of an Energy Component with general equation of state
Physical Review Letters, 1998Co-Authors: Robert R Caldwell, R Dave, Paul J SteinhardtAbstract:We examine the possibility that a significant Component of the Energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ( $\ensuremath{\Lambda}$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this Component alters cosmic evolution in a way that fits current observations well. Unlike $\ensuremath{\Lambda}$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.
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cosmological imprint of an Energy Component with general equation of state
Physical Review Letters, 1998Co-Authors: Robert R Caldwell, R Dave, Paul J SteinhardtAbstract:We examine the possibility that a significant Component of the Energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ({Lambda} ). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this Component alters cosmic evolution in a way that fits current observations well. Unlike {Lambda} , it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum. {copyright} {ital 1998} {ital The American Physical Society}
Robert R Caldwell - One of the best experts on this subject based on the ideXlab platform.
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effects of the sound speed of quintessence on the microwave background and large scale structure
Physical Review D, 2003Co-Authors: Simon Dedeo, Robert R Caldwell, Paul J SteinhardtAbstract:One of the greatest challenges in cosmology today is to identify the nature of the dark Energy Component that comprises most of the Energy density of the universe and that is causing the expansion of the universe to accelerate.[1] Two candidates are a cosmological constant (or vacuum density) and quintessence,[2] a dynamical Energy Component with negative pressure. Distinguishing the two is important for cosmology in order to refine our knowledge of the composition of the universe and to trace more accurately its evolution. It is even more important for fundamental physics since it informs us how we must modify unified theories to incorporate dark Energy.
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a phantom menace cosmological consequences of a dark Energy Component with super negative equation of state
Physics Letters B, 2002Co-Authors: Robert R CaldwellAbstract:Abstract It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort to explain this current state has focused attention on cosmological models in which the dominant Component of the cosmic Energy density has negative pressure, with an equation of state w⩾−1. Remarking that most observations are consistent with models right up to the w=−1 or cosmological constant (Λ) limit, it is natural to ask what lies on the other side, at w
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a phantom menace cosmological consequences of a dark Energy Component with super negative equation of state
arXiv: Astrophysics, 1999Co-Authors: Robert R CaldwellAbstract:It is extraordinary that a number of observations indicate that we live in a spatially flat, low matter density Universe, which is currently undergoing a period of accelerating expansion. The effort to explain this current state has focused attention on cosmological models in which the dominant Component of the cosmic Energy density has negative pressure, with an equation of state $w \ge -1$. Remarking that most observations are consistent with models right up to the $w=-1$ or cosmological constant ($\Lambda$) limit, it is natural to ask what lies on the other side, at $w<-1$. In this regard, we construct a toy model of a ``phantom'' Energy Component which possesses an equation of state $w<-1$. Such a Component is found to be compatible with most classical tests of cosmology based on current data, including the recent type 1a SNe data as well as the cosmic microwave background anisotropy and mass power spectrum. If the future observations continue to allow $w<-1$, then barring unanticipated systematic effects, the dominant Component of the cosmic Energy density may be stranger than anything expected.
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cosmological imprint of an Energy Component with general equation of state
Physical Review Letters, 1998Co-Authors: Robert R Caldwell, R Dave, Paul J SteinhardtAbstract:We examine the possibility that a significant Component of the Energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ( $\ensuremath{\Lambda}$). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this Component alters cosmic evolution in a way that fits current observations well. Unlike $\ensuremath{\Lambda}$, it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum.
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cosmological imprint of an Energy Component with general equation of state
Physical Review Letters, 1998Co-Authors: Robert R Caldwell, R Dave, Paul J SteinhardtAbstract:We examine the possibility that a significant Component of the Energy density of the Universe has an equation of state different from that of matter, radiation, or cosmological constant ({Lambda} ). An example is a cosmic scalar field evolving in a potential, but our treatment is more general. Including this Component alters cosmic evolution in a way that fits current observations well. Unlike {Lambda} , it evolves dynamically and develops fluctuations, leaving a distinctive imprint on the microwave background anisotropy and mass power spectrum. {copyright} {ital 1998} {ital The American Physical Society}