14,439 research outputs found
Semiclassical vibrational spectroscopy : the importance of quantum anharmonicity in supra-molecular systems
No full textSemiclassical (SC) vibrational spectroscopy has been applied successfully to several molecular systems thanks to the possibility to regain quantum effects accurately starting from short-time classical trajectories.[1-5] Larger molecular and supra-molecular systems represent instead an open challenge in the field of semiclassical spectroscopy mainly due to the necessity to work in very high dimensionality.
To start off the talk I will present some recent theoretical advances able to extend the range of applicability of SC vibrational spectroscopy to very high-dimensional systems.[6-7] Then, I will move to applications of semiclassical spectroscopy concerning the vibrational features of water clusters and two supra-molecular systems involving glycine.[8-9] These applications will point out the importance of a multi-reference, dynamical approach able to reproduce quantum anharmonicities without employing any ad-hoc scaling factor.
[1] M. F. Herman, E. Kluk, Chem. Phys. 1984, 91, 27.
[2] A. L. Kaledin, W. H. Miller, J. Chem. Phys. 2003, 118, 7174.
[3] M. Ceotto, S. Atahan, G. F. Tantardini, A. Aspuru-Guzik, J. Chem. Phys. 2009, 130, 234113.
[4] R. Conte, A. Aspuru-Guzik, M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407.
[5] F. Gabas, R. Conte, M. Ceotto, J. Chem. Theory Comput. 2017, 13, 2378.
[6] M. Ceotto, G. Di Liberto, R. Conte, Phys. Rev. Lett. 2017, 119, 010401.
[7] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 014307.
[8] G. Di Liberto, R. Conte, M. Ceotto, J. Chem. Phys. 2018, 148, 104302.
[9] F. Gabas, G. Di Liberto, R. Conte, M. Ceotto, to be submitted
How many water molecules are needed to solvate one?
No full textThe comprehension at the molecular scale of the processes involved during solvation still remains a challenge in chemistry. Remarkably, the question concerning how many solvent molecules are necessary to solvate a solute one is still open. By exploring several water clusters of increasing size, we employ semiclassical spectroscopy [1-5] to determine on quantum dynamical grounds the minimal number of surrounding water molecules to make the central one display the same vibrational features of liquid water. We find out that the minimal structure eventually responsible of proper solvation is made of 21 water molecules, and that particular care must be reserved to the quantum description of the combination of the central monomer bending mode with network low-frequency librations.[6] The results obtained with the accurate ab initio potential are then compared with the popular Caldeira-Leggett one to rationalize whether a simplified model can qualitatively and quantitatively describe the solvated system behavior.[7] An ongoing study on how genetic algorithms[8] and adiabatically switched trajectories[9] can help to deconstruct the complex spectrum of the formic acid dimer will be also presented.
[1] E. J. Heller, Acc. Chem. Res. 14, 368-375 (1981).
[2] M. F. Herman and E. Kluk, Chem. Phys. 91, 27-34 (1984).
[3] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 119, 3078-3084 (2003).
[4] M. Ceotto, S. Atahan, G. F. Tantardini and A. Aspuru-Guzik, J. Chem. Phys. 130, 234113 (2009).
[5] M. Ceotto, G. Di Liberto and R. Conte, Phys. Rev. Lett. 119, 010401 (2017).
[6] A. Rognoni, R. Conte and M. Ceotto, Chem. Sci. 12, 2060 (2021).
[7] A. Rognoni, R. Conte and M. Ceotto, J. Chem. Phys. 154, 094106 (2021). [8] M. Gandolfi, A. Rognoni, C. Aieta, R. Conte and M Ceotto, J. Chem. Phys. 153, 204104 (2020). [9] R. Conte, L. Parma, C. Aieta, A. Rognoni and M. Ceotto, J. Chem. Phys. 151, 214107 (2019)
Opere del conte Algarotti.
No full textIncludes index in vol. 7.Added t.p. in vol. 1, engraved by Giuseppe Patrini. Engraved portrait medallion of the author on t.p. in vol. 1, small woodcut title-vignettes on title pages in vol. 2-10.Mode of access: Internet
Defining civil and political rights: the jurisprudence of the United Nations Human Rights Committee
No full textContentsProcedure under the optional protocol, Scott Davidson; Self-determination, Richard Burchill; Democratic and civil rights, Alex Conte; Security of the person, Alex Conte; The judicial process, Alex Conte; Privacy, honour and reputation, Alex Conte; Equality and non-discrimination, Scott Davidson; Minority rights, Richard Burchill; Rights of the family and children, Richard Burchill; Appendix 1: international covenant on civil and political rights; Appendix 2: optional protocol to the international covenant on civil and political rights; Appendix 3: ratification status of the international covenant on civil and political rights and its optional protocol; Appendix 4: model complaint for
Investigating molecular quantum vibrational frequencies with semiclassical dynamics: theory and application to systems of astrochemical interest
No full textSemiclassical (SC) dynamics allows to regain quantum effects starting from short-time classical trajectories. This feature makes it an attractive and promising tool for accurate spectroscopy investigations, which cannot neglect quantum effects. To start off I will briefly review the main SC approaches employed in vibrational spectroscopy including very recent advances to extend the range of applicability of SC dynamics to large molecular and supra-molecular systems.[1-6] Then, I will present an application of the SC theory to the astrochemically relevant glycine molecule.[7] Finally, the semiclassical study of supra-molecular systems involving glycine will demonstrate the importance in vibrational spectroscopy of an approach able to account for quantum anharmonicity over the commonly employed procedures based on an ad hoc scaling of the harmonic frequencies.
1. M. F. Herman and E. Kluk, Chem. Phys. 91, 27 (1984).
2. A. L. Kaledin and W. H. Miller, J. Chem. Phys. 118, 7174 (2003).
3. M. Ceotto, S. Atahan, G. F. Tantardini, and A. Aspuru-Guzik, J. Chem. Phys. 130, 234113 (2009).
4. R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 4, 3407 (2013).
5. M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 119, 010401 (2017).
6. G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 148, 014307 (2018).
7. F. Gabas, R. Conte, and M. Ceotto, J. Chem. Theory Comput. 13, 2378 (2017)
A Time Averaged Semiclassical Approach to IR Spectroscopy
No full textSemiclassical vibrational spectroscopy is based on the evolution of classical trajectories and is able to reproduce quantum effects with good accuracy at the cost of a reasonable computational effort. [1-5] Nevertheless, semiclassical vibrational power spectra do not simulate all the features of the experimental IR spectra, since intensities in power spectra are not directly related to IR absorptions. Therefore, we
developed a new semiclassical approach to the calculation of molecular IR spectra by employing the time average technique upon symmetrization of the quantum dipole-dipole autocorrelation function. [6,7] We tested the accuracy of this new method on a few simple analytical systems and small molecules in the gas phase. In particular, spectra in the limit of infinite or zero temperature were investigated. Overall the method features excellent accuracy in calculating absorption intensities and provides estimates for the frequencies of vibrations in agreement with the corresponding power spectra.
[1] R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 4, 3407 (2013).
[2] G. Bertaina, G. Di Liberto, and M. Ceotto, J. Chem. Phys. 151, 114307 (2019).
[3] C. Aieta, M. Micciarelli, G. Bertaina, and M. Ceotto, Nat. Comm. 11, 4384 (2020).
[4] A. Rognoni, R. Conte, and M. Ceotto, Chem. Sci. 12, 2060 (2021).
[5] R. Conte, C. Aieta, G. Botti, M. Cazzaniga, M. Gandolfi, C. Lanzi, G. Mandelli, D. Moscato, and M. Ceotto, Theor. Chem. Acc. 142, 53 (2023).
[6] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 118, 7174 (2003).
[7] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 119, 3078 (2003)
Semiclassical Molecular Dynamics for Spectroscopic Calculations of Complex Systems
No full textI will present some novel semiclassical methods for spectroscopic calculations. These approaches can be employed for spectroscopic calculations of gas-phase molecular and supramolecular systems
up to hundreds of degrees of freedom, as well as to condensed phase systems. Some methods are based on a “divide-and-conquer” approach, where the full dimensional spectra are obtained as a
composition of several lower dimensional ones. Others exploit hierarchically the different levels of accuracy of different semiclassical propagators. For instance, in a system-bath problem lower
semiclassical accuracy is dedicated to the bath, while the system is treated with higher accuracy and the system spectrum is eventually singled out.
All methods are amenable for ab initio molecular dynamics simulations.
References
1. F. Gabas, G. Di Liberto, R. Conte, and M. Ceotto, Chemical Science 9 (41), 7885-8026 (2018);
2. X. Ma, G. Di Liberto, R. Conte, W. L. Hase, and M. Ceotto, JCP 149, 164113 (2018)
3. M. Micciarelli, R. Conte, J. Suarez, and M. Ceotto, JCP 149, 064115 (2018);
4. M. Buchholz, F. Grossmann, and M. Ceotto, JCP 148, 114107 (2018);
5. G. Di Liberto, R. Conte, and M. Ceotto, JCP 148, 104302 (2018);
6. G. Di Liberto, R. Conte, and M. Ceotto, JCP 148, 014307 (2018);
7. M. Buchholz, F. Grossmann, and M. Ceotto, JCP 147, 164110 (2017);
8. M. Ceotto, G. Di Liberto, and R. Conte, PRL 119, 010401 (2017);
9. F. Gabas, R. Conte, and M. Ceotto, JCTC 13, 2378-2388 (2017);
10. G. Di Liberto, M. Ceotto, JCP 145, 144107 (2016);
11. M. Buchholz, F. Grossmann, M. Ceotto, JCP 144, 094102 (2016)
Divide-and-Conquer Semiclassical Dynamics: A Viable Method for Vibrational Spectra Calculations of High Dimensional and Anharmonic Molecular Systems
No full textThe prediction of accurate vibrational frequencies is often necessary for the interpretation of experimental outcomes, especially when sources of strong anharmonic effects such as hydrogen bonding are present. Unfortunately, the most relevant stumbling block to fill in the gap between theory and experiment is usually represented by dimensionality problems, when quantum mechanical effects like Zero Point Energy, quantum anharmonicities, and overtones cannot be neglected. In this circumstance quantum applications are generally limited to small and medium sized molecules. One possible alternative is represented by Semiclassical theory, which allows to recover accurate spectral densities by taking advantage of quantities arising from classical mechanics simulations. [1-5] In particular, here we present a method, called Semiclassical “Divide-and-Conquer”, able to reproduce spectra of high-dimensional molecular systems accurately. [6,7] The method is first validated by performing spectra of small and medium sized molecules, and then it is used to calculate the spectra of benzene and a C 60 model, which is made of 174 degrees of freedom. Then, we show results of variously sized-water clusters characterized by strong hydrogen-bonding that red shifts the involved OH stretches. [8] Finally, the method is combined with ab-initio molecular dynamics to abandon the necessity to employ pre-fitted Potential Energy Surfaces, and applied to study supramolecular systems like the protonated glycine dimer and hydrogen-tagged protonated glycine. [9] [1] W. H. Miller, J. Chem. Phys. 1970, 53, 3578;
[2] E. J. Heller, J. Chem. Phys. 1981, 75, 2923; M. F. Herman and E. Kluk, Chem. Phys. 1984, 91, 27.
[3] K. G. Kay, J. Chem. Phys. 1994, 101, 2250; W. H. Miller, J. Phys. Chem. A 2001, 105, 2942.
[4] A. L. Kaledin and W. H. Miller, J. Chem. Phys. 2003, 118, 7174.
[5] R. Conte, A. Aspuru-Guzik, and M. Ceotto, J. Phys. Chem. Lett. 2013, 4, 3407.
[6] M. Ceotto, G. Di Liberto, and R. Conte, Phys. Rev. Lett. 2017, 119, 010401.
[7] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 014307.
[8] G. Di Liberto, R. Conte, and M. Ceotto, J. Chem. Phys. 2018, 148, 104302.
[9] F. Gabas, G. Di Liberto, R. Conte, and M. Ceotto In preparation
Quantum Mechanical Methods for Spectroscopic Calculations of High Dimensional Molecular Systems
No full textI will present some novel semiclassical methods for spectroscopic calculations. These approaches can be employed for spectroscopic calculations of gas-phase molecular and supramolecular systems
up to hundreds of degrees of freedom, as well as to condensed phase systems. Some methods are based on a “divide-and-conquer” approach, where the full dimensional spectra are obtained as a
composition of several lower dimensional ones. Others exploit hierarchically the different levels of accuracy of different semiclassical propagators.
All methods are amenable to ab initio molecular dynamics simulations.
References
1. M. Micciarelli, R. Conte, J. Suarez, and M. Ceotto, JCP 149, 064115 (2018);
2. M. Buchholz, F. Grossmann, and M. Ceotto, JCP 148, 114107 (2018);
3. G. Di Liberto, R. Conte, and M. Ceotto, JCP 148, 104302 (2018);
4. G. Di Liberto, R. Conte, and M. Ceotto, JCP 148, 014307 (2018);
5. M. Buchholz, F. Grossmann, and M. Ceotto, JCP 147, 164110 (2017);
6. M. Ceotto, G. Di Liberto, and R. Conte, PRL 119, 010401 (2017);
7. F. Gabas, R. Conte, and M. Ceotto, JCTC 13, 2378-2388 (2017);
8. G. Di Liberto, M. Ceotto, JCP 145, 144107 (2016);
9. M. Buchholz, F. Grossmann, M. Ceotto, JCP 144, 094102 (2016)
Petit conte : valse facile pour piano / par R. Arenal
No full textTitre uniforme : Arenal, R. (18..-19.. ; compositeur). Compositeur. [Petit conte. Piano]Valses (piano) -- +* 1900......- 1999......+:20e siècle:Piano, Musique de -- +* 1900......- 1999......+:20e siècle
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