Stability of polar guest-encaging clathrate hydrates

Kenichiro Koga, Hideki Tanaka, Koichiro Nakanishi

Research output: Contribution to journalArticle

16 Citations (Scopus)

Abstract

In order to account for the experimental observation that some amines form clathrate hydrates but that alcohols inhibit hydrate formation, we investigate the stability of clathrate hydrates which encage highly polar guest molecules by examining potential energy local minimum structures and also thermally excited structures. First, we examine the local minimum structure at which the total potential energy has a minimum value for amine and alcohol hydrates and inquire whether, in the absence of thermal fluctuations, the conditions for true-clathrate hydrates are satisfied. The local minimum structures of alcohol hydrates are distinguished from those of stable clathrate hydrates of structures I and II, while amine hydrates hold the host lattice of clathrate hydrates. We argue that the difference between the magnitude of the partial charge on the hydrogen atom of the hydroxyl and amino groups plays a much more significant role in the stability of both kinds of clathrate hydrates than the difference in molecular geometry does. Second, we examine kinetic stability by molecular dynamics simulation. Near room temperature the host lattice structure encaging amine remains intact. This is in contrast to the alcohol hydrate, which begins to melt easily with thermal excitation. Interesting is the finding that very long-time-scale (∼100 ps) fluctuations of the host potential energy is observed, as well as fast oscillations caused by temporary partial defects in the host network. Clathrate hydrates of polar guest molecules may experience an unstable state in which the host hydrogen-bonded network is partially broken and guest-host hydrogen-bond generation occurs but the stable state of their host lattices is again restored.

Original languageEnglish
Pages (from-to)3127-3134
Number of pages8
JournalThe Journal of Chemical Physics
Volume101
Issue number4
Publication statusPublished - 1994
Externally publishedYes

Fingerprint

clathrates
Hydrates
hydrates
Amines
amines
alcohols
Potential energy
Alcohols
potential energy
Hydrogen
Molecules
Hydroxyl Radical
Molecular dynamics
molecules
hydrogen atoms
Hydrogen bonds
hydrogen bonds
molecular dynamics

ASJC Scopus subject areas

  • Atomic and Molecular Physics, and Optics

Cite this

Stability of polar guest-encaging clathrate hydrates. / Koga, Kenichiro; Tanaka, Hideki; Nakanishi, Koichiro.

In: The Journal of Chemical Physics, Vol. 101, No. 4, 1994, p. 3127-3134.

Research output: Contribution to journalArticle

@article{f78e3038b61b425d9f03d572cd597c64,
title = "Stability of polar guest-encaging clathrate hydrates",
abstract = "In order to account for the experimental observation that some amines form clathrate hydrates but that alcohols inhibit hydrate formation, we investigate the stability of clathrate hydrates which encage highly polar guest molecules by examining potential energy local minimum structures and also thermally excited structures. First, we examine the local minimum structure at which the total potential energy has a minimum value for amine and alcohol hydrates and inquire whether, in the absence of thermal fluctuations, the conditions for true-clathrate hydrates are satisfied. The local minimum structures of alcohol hydrates are distinguished from those of stable clathrate hydrates of structures I and II, while amine hydrates hold the host lattice of clathrate hydrates. We argue that the difference between the magnitude of the partial charge on the hydrogen atom of the hydroxyl and amino groups plays a much more significant role in the stability of both kinds of clathrate hydrates than the difference in molecular geometry does. Second, we examine kinetic stability by molecular dynamics simulation. Near room temperature the host lattice structure encaging amine remains intact. This is in contrast to the alcohol hydrate, which begins to melt easily with thermal excitation. Interesting is the finding that very long-time-scale (∼100 ps) fluctuations of the host potential energy is observed, as well as fast oscillations caused by temporary partial defects in the host network. Clathrate hydrates of polar guest molecules may experience an unstable state in which the host hydrogen-bonded network is partially broken and guest-host hydrogen-bond generation occurs but the stable state of their host lattices is again restored.",
author = "Kenichiro Koga and Hideki Tanaka and Koichiro Nakanishi",
year = "1994",
language = "English",
volume = "101",
pages = "3127--3134",
journal = "Journal of Chemical Physics",
issn = "0021-9606",
publisher = "American Institute of Physics Publising LLC",
number = "4",

}

TY - JOUR

T1 - Stability of polar guest-encaging clathrate hydrates

AU - Koga, Kenichiro

AU - Tanaka, Hideki

AU - Nakanishi, Koichiro

PY - 1994

Y1 - 1994

N2 - In order to account for the experimental observation that some amines form clathrate hydrates but that alcohols inhibit hydrate formation, we investigate the stability of clathrate hydrates which encage highly polar guest molecules by examining potential energy local minimum structures and also thermally excited structures. First, we examine the local minimum structure at which the total potential energy has a minimum value for amine and alcohol hydrates and inquire whether, in the absence of thermal fluctuations, the conditions for true-clathrate hydrates are satisfied. The local minimum structures of alcohol hydrates are distinguished from those of stable clathrate hydrates of structures I and II, while amine hydrates hold the host lattice of clathrate hydrates. We argue that the difference between the magnitude of the partial charge on the hydrogen atom of the hydroxyl and amino groups plays a much more significant role in the stability of both kinds of clathrate hydrates than the difference in molecular geometry does. Second, we examine kinetic stability by molecular dynamics simulation. Near room temperature the host lattice structure encaging amine remains intact. This is in contrast to the alcohol hydrate, which begins to melt easily with thermal excitation. Interesting is the finding that very long-time-scale (∼100 ps) fluctuations of the host potential energy is observed, as well as fast oscillations caused by temporary partial defects in the host network. Clathrate hydrates of polar guest molecules may experience an unstable state in which the host hydrogen-bonded network is partially broken and guest-host hydrogen-bond generation occurs but the stable state of their host lattices is again restored.

AB - In order to account for the experimental observation that some amines form clathrate hydrates but that alcohols inhibit hydrate formation, we investigate the stability of clathrate hydrates which encage highly polar guest molecules by examining potential energy local minimum structures and also thermally excited structures. First, we examine the local minimum structure at which the total potential energy has a minimum value for amine and alcohol hydrates and inquire whether, in the absence of thermal fluctuations, the conditions for true-clathrate hydrates are satisfied. The local minimum structures of alcohol hydrates are distinguished from those of stable clathrate hydrates of structures I and II, while amine hydrates hold the host lattice of clathrate hydrates. We argue that the difference between the magnitude of the partial charge on the hydrogen atom of the hydroxyl and amino groups plays a much more significant role in the stability of both kinds of clathrate hydrates than the difference in molecular geometry does. Second, we examine kinetic stability by molecular dynamics simulation. Near room temperature the host lattice structure encaging amine remains intact. This is in contrast to the alcohol hydrate, which begins to melt easily with thermal excitation. Interesting is the finding that very long-time-scale (∼100 ps) fluctuations of the host potential energy is observed, as well as fast oscillations caused by temporary partial defects in the host network. Clathrate hydrates of polar guest molecules may experience an unstable state in which the host hydrogen-bonded network is partially broken and guest-host hydrogen-bond generation occurs but the stable state of their host lattices is again restored.

UR - http://www.scopus.com/inward/record.url?scp=0001675941&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0001675941&partnerID=8YFLogxK

M3 - Article

AN - SCOPUS:0001675941

VL - 101

SP - 3127

EP - 3134

JO - Journal of Chemical Physics

JF - Journal of Chemical Physics

SN - 0021-9606

IS - 4

ER -