Magic numbers for water-ammonia binary clusters: Enhanced stability of ion clathrate structures

Hisanori Shinohara, Umpei Nagashima, Hideki Tanaka, Nobuyuki Nishi

Research output: Contribution to journalArticle

76 Citations (Scopus)

Abstract

The formation of water-ammonia binary clusters (H2O)n (NH3)m H+ (q≲40, q = n + m), have been investigated employing a neutral supersonic nozzle expansion of premixed water-ammonia gas with molecular-beam-mass spectrometry. The analysis of the mass spectra reveals that the number of water-rich clusters is greatly increased as the cluster size is increased. Mass spectroscopic evidence for the existence of enhanced structural stabilities ("magic numbers") has been found at the protonated clusters (H2O)20(NH3) m H+ (m = 1-6) and (H2O)27NH 4+. Considerations for the magic number stabilities are presented within the framework of ion clathrate (ion-centered cage) structures. Monte Carlo simulations are also presented for ionized (protonated) clusters around n = 20 and n = 27 with m = 1. The clusters (H2O) 20NH4+ and (H2O)27NH 4+ have greater binding energies per molecule than their neighbors, in agreement with the mass spectroscopic observations. The calculated structure for (H2O)20NH4+ also indicates the stability of pentagonal rings of water molecules and deformed dodecahedral structure with an NH4+ ion trapped inside; the cluster is especially stable due not only to the strong Coulombic interaction (ionic hydrogen bonding) between the NH4+ ion and the surrounding 20 water molecules but to hydrogen bonding networks forming the cage structure. The proposed ion-centered cage model can also explain satisfactorily the well-known stability of the water cluster of (H 2O)20H3O+.

Original languageEnglish
Pages (from-to)4183-4192
Number of pages10
JournalThe Journal of Chemical Physics
Volume83
Issue number8
Publication statusPublished - 1985
Externally publishedYes

Fingerprint

clathrates
Ammonia
ammonia
Ions
Water
water
ions
Molecules
Hydrogen bonds
Trapped ions
Molecular beams
Binding energy
supersonic nozzles
molecules
Mass spectrometry
Nozzles
structural stability
hydrogen
Gases
molecular beams

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Magic numbers for water-ammonia binary clusters : Enhanced stability of ion clathrate structures. / Shinohara, Hisanori; Nagashima, Umpei; Tanaka, Hideki; Nishi, Nobuyuki.

In: The Journal of Chemical Physics, Vol. 83, No. 8, 1985, p. 4183-4192.

Research output: Contribution to journalArticle

Shinohara, Hisanori ; Nagashima, Umpei ; Tanaka, Hideki ; Nishi, Nobuyuki. / Magic numbers for water-ammonia binary clusters : Enhanced stability of ion clathrate structures. In: The Journal of Chemical Physics. 1985 ; Vol. 83, No. 8. pp. 4183-4192.
@article{f04d71d0d3fe466f84a2b64b8212ab75,
title = "Magic numbers for water-ammonia binary clusters: Enhanced stability of ion clathrate structures",
abstract = "The formation of water-ammonia binary clusters (H2O)n (NH3)m H+ (q≲40, q = n + m), have been investigated employing a neutral supersonic nozzle expansion of premixed water-ammonia gas with molecular-beam-mass spectrometry. The analysis of the mass spectra reveals that the number of water-rich clusters is greatly increased as the cluster size is increased. Mass spectroscopic evidence for the existence of enhanced structural stabilities ({"}magic numbers{"}) has been found at the protonated clusters (H2O)20(NH3) m H+ (m = 1-6) and (H2O)27NH 4+. Considerations for the magic number stabilities are presented within the framework of ion clathrate (ion-centered cage) structures. Monte Carlo simulations are also presented for ionized (protonated) clusters around n = 20 and n = 27 with m = 1. The clusters (H2O) 20NH4+ and (H2O)27NH 4+ have greater binding energies per molecule than their neighbors, in agreement with the mass spectroscopic observations. The calculated structure for (H2O)20NH4+ also indicates the stability of pentagonal rings of water molecules and deformed dodecahedral structure with an NH4+ ion trapped inside; the cluster is especially stable due not only to the strong Coulombic interaction (ionic hydrogen bonding) between the NH4+ ion and the surrounding 20 water molecules but to hydrogen bonding networks forming the cage structure. The proposed ion-centered cage model can also explain satisfactorily the well-known stability of the water cluster of (H 2O)20H3O+.",
author = "Hisanori Shinohara and Umpei Nagashima and Hideki Tanaka and Nobuyuki Nishi",
year = "1985",
language = "English",
volume = "83",
pages = "4183--4192",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "8",

}

TY - JOUR

T1 - Magic numbers for water-ammonia binary clusters

T2 - Enhanced stability of ion clathrate structures

AU - Shinohara, Hisanori

AU - Nagashima, Umpei

AU - Tanaka, Hideki

AU - Nishi, Nobuyuki

PY - 1985

Y1 - 1985

N2 - The formation of water-ammonia binary clusters (H2O)n (NH3)m H+ (q≲40, q = n + m), have been investigated employing a neutral supersonic nozzle expansion of premixed water-ammonia gas with molecular-beam-mass spectrometry. The analysis of the mass spectra reveals that the number of water-rich clusters is greatly increased as the cluster size is increased. Mass spectroscopic evidence for the existence of enhanced structural stabilities ("magic numbers") has been found at the protonated clusters (H2O)20(NH3) m H+ (m = 1-6) and (H2O)27NH 4+. Considerations for the magic number stabilities are presented within the framework of ion clathrate (ion-centered cage) structures. Monte Carlo simulations are also presented for ionized (protonated) clusters around n = 20 and n = 27 with m = 1. The clusters (H2O) 20NH4+ and (H2O)27NH 4+ have greater binding energies per molecule than their neighbors, in agreement with the mass spectroscopic observations. The calculated structure for (H2O)20NH4+ also indicates the stability of pentagonal rings of water molecules and deformed dodecahedral structure with an NH4+ ion trapped inside; the cluster is especially stable due not only to the strong Coulombic interaction (ionic hydrogen bonding) between the NH4+ ion and the surrounding 20 water molecules but to hydrogen bonding networks forming the cage structure. The proposed ion-centered cage model can also explain satisfactorily the well-known stability of the water cluster of (H 2O)20H3O+.

AB - The formation of water-ammonia binary clusters (H2O)n (NH3)m H+ (q≲40, q = n + m), have been investigated employing a neutral supersonic nozzle expansion of premixed water-ammonia gas with molecular-beam-mass spectrometry. The analysis of the mass spectra reveals that the number of water-rich clusters is greatly increased as the cluster size is increased. Mass spectroscopic evidence for the existence of enhanced structural stabilities ("magic numbers") has been found at the protonated clusters (H2O)20(NH3) m H+ (m = 1-6) and (H2O)27NH 4+. Considerations for the magic number stabilities are presented within the framework of ion clathrate (ion-centered cage) structures. Monte Carlo simulations are also presented for ionized (protonated) clusters around n = 20 and n = 27 with m = 1. The clusters (H2O) 20NH4+ and (H2O)27NH 4+ have greater binding energies per molecule than their neighbors, in agreement with the mass spectroscopic observations. The calculated structure for (H2O)20NH4+ also indicates the stability of pentagonal rings of water molecules and deformed dodecahedral structure with an NH4+ ion trapped inside; the cluster is especially stable due not only to the strong Coulombic interaction (ionic hydrogen bonding) between the NH4+ ion and the surrounding 20 water molecules but to hydrogen bonding networks forming the cage structure. The proposed ion-centered cage model can also explain satisfactorily the well-known stability of the water cluster of (H 2O)20H3O+.

UR - http://www.scopus.com/inward/record.url?scp=0000597026&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0000597026&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0000597026

VL - 83

SP - 4183

EP - 4192

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 8

ER -