Vibrational frequencies of guest molecules in clathrate hydrates reflect the molecular environment and dynamical behavior of molecules. A detailed understanding of the mechanism for the vibrational frequency changes of the guest molecules in the clathrate hydrate cages is still incomplete. In this study, molecular vibrations of methane molecules in a structure I clathrate hydrate are calculated from ab initio molecular dynamics simulation. The vibrational spectra of methane are computed by Fourier transform of autocorrelation functions, which reveal distinct separation of each vibrational mode. Calculated symmetric and asymmetric stretching vibrational frequencies of methane molecules are lower in the large cages than in the small cages (8 and 16 cm−1 for symmetric and asymmetric stretching, respectively). These changes are closely linked with the C–H bond length. The vibrational frequencies for the bending and rocking vibrational modes nearly overlap in each of the cages.

1.
H.
Lee
,
J.-W.
Lee
,
D. Y.
Kim
,
J.
Park
,
Y.-T.
Seo
,
H.
Zeng
,
I. L.
Moudrakovski
,
C. I.
Ratcliffe
, and
J. A.
Ripmeester
,
Nature (London)
434
,
743
(
2005
).
2.
J. M.
Schicks
and
J. A.
Ripmeester
,
Angew. Chem., Int. Ed.
3
,
3310
(
2004
).
3.
W. L.
Mao
,
H.
Mao
,
A. F.
Goncharov
,
V. V.
Struzhkin
,
Q.
Guo
,
J.
Hu
,
J.
Shu
,
R. J.
Hemley
,
M.
Somayazulu
, and
Y.
Zhao
,
Science
297
,
2247
(
2002
).
4.
A.
Monreal
,
L.
Cwiklik
,
B.
Jagoda-Cwiklik
, and
J. P.
Devlin
,
J. Phys. Chem. Lett.
1
,
290
(
2010
).
5.
K. A.
Kvenvolden
,
Proc. Natl. Acad. Sci. U.S.A.
96
,
3420
(
1999
).
6.
E. D.
Sloan
 Jr.
,
Nature (London)
426
,
353
(
2003
).
7.
A. K.
Sum
,
R. C.
Burruss
, and
E. D.
Sloan
 Jr.
,
J. Phys. Chem. B
101
,
7371
(
1997
).
8.
G. C.
Pimentel
and
S. W.
Charles
,
Pure Appl. Chem.
7
,
111
(
1963
).
9.
S.
Subramanian
and
E. D.
Sloan
 Jr.
,
J. Phys. Chem. B
106
,
4348
(
2002
).
10.
H.
Itoh
and
K.
Kawamura
,
Ann. N.Y. Acad. Sci.
912
,
693
(
2000
).
11.
J. A.
Greathouse
,
R. T.
Cygan
, and
B. A.
Simmons
,
J. Phys. Chem. B
110
,
6428
(
2006
).
12.
F.
Castillo-Borja
,
R.
Vazquez-Roman
, and
U. I.
Bravo-Sanchez
,
Mol. Simul.
36
,
229
(
2010
).
13.
T.
Ikeda
and
K.
Terakura
,
J. Chem. Phys.
119
,
6784
(
2003
).
14.
15.
D.
Sánchez-Portal
,
P.
Ordejón
,
E.
Artacho
, and
J. M.
Soler
,
Int. J. Quantum Chem.
65
,
453
(
1997
);
E.
Artacho
,
J. D.
Gale
,
A.
Garcia
,
J.
Junquera
,
P.
Ordejón
, and
D.
Sánchez-Portal
,
J. Phys. Condens. Matter
14
,
2745
(
2002
).
16.
E. B.
Wilson
 Jr.
,
J. C.
Decius
, and
P. C.
Cross
,
Molecular Vibrations
(
Mcgraw-Hill
,
New York/Toronto/London,
1955
).
17.
T.
Shimanouchi
, “Molecular Vibrational Frequencies” in
NIST Chemistry WebBook
, NIST Standard Reference Database Number 69, Eds.
P. J.
Linstrom
and
W. G.
Mallard
,
National Institute of Standards and Technology
,
Gaithersburg MD
, 20899, http://webbook.nist.gov (retrieved January 6,
2012
).
18.
R.
Car
and
M.
Parrinello
,
Phys. Rev. Lett.
55
,
2471
(
1985
).
19.
CPMD, see http://www.cpmd.org/, Copyright IBM Corp 1990–2008, Copyright MPI für Festkörperforschung Stuttgart 1997–2001.
20.
J. P.
Perdew
,
K.
Burke
, and
M.
Ernzerhof
,
Phys. Rev. Lett.
77
,
3865
(
1996
).
21.
N.
Troullier
and
J. L.
Martines
,
Phys. Rev. B
43
,
1993
(
1991
).
22.
L.
Kleinman
and
D. M.
Bylander
,
Phys. Rev. Lett.
48
,
1425
(
1982
).
23.
R. K.
McMullan
and
G. A.
Jeffrey
,
J. Chem. Phys.
42
,
2725
(
1965
).
24.
V. P.
Shpakov
,
J. S.
Tse
,
C. A.
Tulk
,
B.
Kvamme
, and
V. R.
Belosludov
,
Chem. Phys. Lett.
282
,
107
(
1998
).
25.
G.
Román-Pérez
,
M.
Moaied
,
J. M.
Soler
, and
F.
Yndurain
,
Phys. Rev. Lett.
105
,
145901
(
2010
).
26.
R. W.
Williams
and
D.
Malhotra
,
Chem. Phys.
327
,
54
(
2006
).
27.
S.
Grimme
,
J. Comput. Chem.
27
,
1787
(
2006
).
28.
P.
Tangney
and
S.
Scandolo
,
J. Chem. Phys.
116
,
14
(
2002
).
29.
P.
Tangney
,
J. Chem. Phys.
124
,
044111
(
2006
).
30.
I.-F. W.
Kuo
,
C. J.
Mundy
,
M. J.
McGrath
, and
J. I.
Siepmann
,
J. Chem. Theory Comput.
2
,
1274
(
2006
).
31.
M.-P.
Gaigeot
,
Phys. Chem. Chem. Phys.
12
,
3336
(
2010
).
32.
H.
Ohno
,
M.
Kida
,
T.
Sakurai
,
Y.
Iizuka
,
T.
Hondoh
,
H.
Narita
, and
J.
Nagao
,
ChemPhysChem
11
,
3070
(
2010
).
33.
N. J.
English
and
J. M. D.
MacElroy
,
J. Comput. Chem.
24
,
1569
(
2003
).
34.
See supplementary material at http://dx.doi.org/10.1063/1.3677231 for illustrations of the vibrational modes of methane molecule, the definition and calculated results of autocorrelation functions, and animated images of methane molecule in small and large cages.

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