Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8

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Energetics, structural features, polarity, and melting transitions in water clusters containing up to eight molecules were studied using ab initio methods and empirical force field models. Our quantum approach was based on density functional theory performed at the generalized gradient approximation...

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Autor principal:	Rodriguez, J.
Formato:	JOUR
Materias:	Classical molecular dynamics Classical potentials Empirical force fields Generalized gradient approximation level Minimum-energy structures Pre-melting transition Static polarizabilities Thermal fluctuations Dipole moment Hydrogen bonds Isomerization Isomers Melting Molecular dynamics Aggregates
Acceso en línea:	http://hdl.handle.net/20.500.12110/paper_00219606_v110_n18_p9039_Rodriguez
Aporte de:	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA) de Universidad de Buenos Aires

id	todo:paper_00219606_v110_n18_p9039_Rodriguez
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spelling	todo:paper_00219606_v110_n18_p9039_Rodriguez2023-10-03T14:23:57Z Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8 Rodriguez, J. Classical molecular dynamics Classical potentials Empirical force fields Generalized gradient approximation level Minimum-energy structures Pre-melting transition Static polarizabilities Thermal fluctuations Dipole moment Hydrogen bonds Isomerization Isomers Melting Molecular dynamics Aggregates Energetics, structural features, polarity, and melting transitions in water clusters containing up to eight molecules were studied using ab initio methods and empirical force field models. Our quantum approach was based on density functional theory performed at the generalized gradient approximation level. For the specific case of (H2O)6, we selected five conformers of similar energy with different geometries and dipolar moments. For these cases, the cyclic arrangement was found to be the only nonpolar aggregate. For (H2O)8, the most stable structures corresponded to nonpolar, cubic-like, D2d and S4 conformers. Higher energy aggregates exhibit a large spectrum in their polarities. The static polarizability was found to be proportional to the size of the aggregates and presents a weak dependence with the number of hydrogen bonds. In order to examine the influence of thermal fluctuations on the aggregates, we have performed a series of classical molecular dynamics experiments from low temperature up to the melting transition using two different effective pseudopotentials: the TIP4P and MCY models. Minimum energy structures for both classical potentials were found to reproduce reasonably well the results obtained using ab initio methods. Isomerization and phase transitions were monitored by following changes in dipole moments, number of hydrogen bonds and Lindemann's parameter. For (H2O)6 and (H2O)8, the melting transitions were found at Tm≈50 and 160 K, respectively; for both aggregates, we observed premelting transitions between well differentiated conformers as well. © 1999 American Institute of Physics. Fil:Rodriguez, J. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales; Argentina. JOUR info:eu-repo/semantics/openAccess http://creativecommons.org/licenses/by/2.5/ar http://hdl.handle.net/20.500.12110/paper_00219606_v110_n18_p9039_Rodriguez
institution	Universidad de Buenos Aires
institution_str	I-28
repository_str	R-134
collection	Biblioteca Digital - Facultad de Ciencias Exactas y Naturales (UBA)
topic	Classical molecular dynamics Classical potentials Empirical force fields Generalized gradient approximation level Minimum-energy structures Pre-melting transition Static polarizabilities Thermal fluctuations Dipole moment Hydrogen bonds Isomerization Isomers Melting Molecular dynamics Aggregates
spellingShingle	Classical molecular dynamics Classical potentials Empirical force fields Generalized gradient approximation level Minimum-energy structures Pre-melting transition Static polarizabilities Thermal fluctuations Dipole moment Hydrogen bonds Isomerization Isomers Melting Molecular dynamics Aggregates Rodriguez, J. Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
topic_facet	Classical molecular dynamics Classical potentials Empirical force fields Generalized gradient approximation level Minimum-energy structures Pre-melting transition Static polarizabilities Thermal fluctuations Dipole moment Hydrogen bonds Isomerization Isomers Melting Molecular dynamics Aggregates
description	Energetics, structural features, polarity, and melting transitions in water clusters containing up to eight molecules were studied using ab initio methods and empirical force field models. Our quantum approach was based on density functional theory performed at the generalized gradient approximation level. For the specific case of (H2O)6, we selected five conformers of similar energy with different geometries and dipolar moments. For these cases, the cyclic arrangement was found to be the only nonpolar aggregate. For (H2O)8, the most stable structures corresponded to nonpolar, cubic-like, D2d and S4 conformers. Higher energy aggregates exhibit a large spectrum in their polarities. The static polarizability was found to be proportional to the size of the aggregates and presents a weak dependence with the number of hydrogen bonds. In order to examine the influence of thermal fluctuations on the aggregates, we have performed a series of classical molecular dynamics experiments from low temperature up to the melting transition using two different effective pseudopotentials: the TIP4P and MCY models. Minimum energy structures for both classical potentials were found to reproduce reasonably well the results obtained using ab initio methods. Isomerization and phase transitions were monitored by following changes in dipole moments, number of hydrogen bonds and Lindemann's parameter. For (H2O)6 and (H2O)8, the melting transitions were found at Tm≈50 and 160 K, respectively; for both aggregates, we observed premelting transitions between well differentiated conformers as well. © 1999 American Institute of Physics.
format	JOUR
author	Rodriguez, J.
author_facet	Rodriguez, J.
author_sort	Rodriguez, J.
title	Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
title_short	Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
title_full	Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
title_fullStr	Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
title_full_unstemmed	Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8
title_sort	isomerization, melting, and polarity of model water clusters: (h2o)6 and (h2o)8
url	http://hdl.handle.net/20.500.12110/paper_00219606_v110_n18_p9039_Rodriguez
work_keys_str_mv	AT rodriguezj isomerizationmeltingandpolarityofmodelwaterclustersh2o6andh2o8
_version_	1807322923399118848

Isomerization, melting, and polarity of model water clusters: (H2O)6 and (H2O)8

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