v- 20w!)&TSUBAME 6Z !yzZ F6Z !)&6IX = 5' nrjptmoltkqsu 1vEFP-MDwbdfhit2c32,NJ*D%{A theoretical study on solution structure of ionic liquids using Effective Fragment Potential – Moleculardynamics simulation (EFP-MD)+Z #Hirotoshi MORI]Ec08<TC4:@Faculty of Core Research, Ochanomizu UniversityO%"QZ §1¬g^]]dM3&s¬p§¨§jumn&-6~ihHre$=¬[¬[J57"z¬§1+¨Y.¨:Bf U~0@X}jer¬§1w,!§lq¬4W<§1 tqn~ojkg§Kh"|e©1s}'v§1
|j}¬q ~Z>216P*nF >#Tr}oxe%¬w9R>P*(y=S8 i¬ZD|2169R>ON¦¥L{}jje)AC~§1
5 >6¬;QInACV=#Ts}j& ¤¢§ §£¥\ /ª`ac\b_«?¬E9>§169RON©¡V=Gye
D % " Q Z Ionic liquids are highly stable, heat-resistant, and non-volatile solvents that areimportant in industrial fields. Conventionally, classical MD has been used to understand thesolution structure of ionic liquids. However, even some classical force fields have been reported forspecific ionic liquids with great efforts, we cannot apply them for designing novel ionic liquids in adirect manner. In the backgrounds, ab initio MD, which does not need any pre-optimized force fieldparameters, has gradually caught attention with the growth of high-performance computers.
However, its computational cost is extremely higher than the classical one. Thus, a method having
both high chemical accuracy and low computational cost is strongly required. In this study, weinvestigated the possibility of effective fragment potential MD theory for describing thermodynamic
properties of ionic liquids.

Keywords: hit2['nrjptmoltkqs[EFP
MDEFPEFPv- 20w!)&GAMESSGAMESS

MP2/aug-cc-pVDZ

EFP-MD
RHF/aug-cc-pVDZ [mmim]+ Cl- Br-

RHF/(DK3-)SPK-(aug-)cc-pVDZ IEFP2[mmim]+EFP2

ClI

Br-

EFP2

-

EFP2

RHF/SPK-cc-pVDZ[mmim]+[mmim]+Hardacre[mmim]+

D

RHF/DK3-SPK-cc-pVDZ

rD

RHF/SPK-aug-cc-pVDZ

AD

RHF/DK3-SPK-aug-cc-pVDZrAD

GAMESSEFP c?9H[mmim]Cl
ClI

Br-[mmim]Br[mmim]I

1+[mmim] … X--[mmim]ClEFP2[mmim]Br[mmim]I1

EFP2[mmim]+xyz

11MP2/aug-cc-pVDZXGAMESS

Gaussian09

H2(C6(C2N1(27MP2/SPK-aug-cc-pVTZ

C5(finite field

H5(I-1model core potential MCP
MP2/MCP-aug-cc-pVTZ
GAMESSEFPz

N3(EFP2
LMO-EDAC4(H4([mmim]+C7(xv- 20w!)&BSSE

Counter-Poise
Gaussian09

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or(DK3-)SPK-(aug-)cc-pVDZ
MOE2014

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EFP2 2Z EFP2-MD G>c(,NGAMESSEFP2-MD
EFP2-MDT = 298 K 1 fs/step

8,000

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EFP2
16 CPU Core 2.60 GHz Intel(R)T = 425 K

5 fs/step

200,000

1 ns

Xeon(R) CPU E5-2670
EFP2
1N
packmol
emim+Cl- 1.12 g cm-3 298 K
1.39 g cm
× 18.3 3-3

298 K

emim+Br-

2T (t)2 − T (t) tt

2

18.3 × 18.3

T (t) t=23N

33250,0002Å

250 psEFP2-MD
EFP2

MOE2014GAMESS

EFP25Ewald

EFP2-MD
NVT
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5 fs
EFP2-MDv- 20w!)&1[mmim]+2MP2/aug-cc-pVDZ
53I-dBr-1.53model core potential

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C4 C5MCP-Ip-

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H5y

T = 425 K

C2-H2250 ps

C4-H4

NVT
EFP2-MDRDF

C5-H5CPMD

89

4 5z

RDF

H2
C2

C6

C7z
C5
H5

EFP2-MDx

R = 17 ÅxC4g(R)

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1

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v- 20w!)&J. Phys. Chem. B, Vol. 109, No. 39, 2005 18597
J. Phys. Chem. B, Vol. 109, No. 39, 2005 18597[mmim]Cl6""

実験結果

C2#X#
C4#X#
C5#X#'
C6#X#'
C7#X#

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mmim]+%Cl%
mmim]+%mmim]+

2""
0""
2""
CPMD

4""

8"" 10"" 12"" 14"" 16""[mmim]Br6""[mmim]+%Cl%
[mmim]+%[mmim]+

6""

4""
2""
0""
2""

4""

[mmim]Cl

6""
4""

8"" 10"" 12"" 14"" 16""[mmim]ID

6""[mmim]+%X%
[mmim]+%[mmim]+
X%%X%

6""

4""

2""

2""
0""
2""

4""

6""

8"" 10"" 12"" 14"" 16""

0""
2""

4""

6""

8"" 10"" 12"" 14"" 16""[mmim]Br6""

 5Z EFP2-MD G>bd_`eg^ RDF
4""

BL{7SS$ g(R)x.L{

hit;RKU

R2""

40""
2""

4""

6""

8"" 10"" 12"" 14"" 16""

EFP2-MD[mmim]ClRDF

RDF

Figure 9. Radial6""
distribution functions Dfor the cation-cation (circleFigure 9. Radial distribution [mmim]I
functions for the cation-cation (circle+ line) and cation-anion (line) distribution extracted from simulations+ line) and cation-anion (line) distribution extracted from simulationsof larger boxes; from top to bottom: Experimental data derived in refof larger boxes; from top to bottom: Experimental data derived in ref
16 (reprinted with permission. Copyright 2003, American Institute of
16 (reprinted with4""permission. Copyright 2003, American Institute ofPhysics). Simulations of 41 ion pairs (box 2), and of 300 ion pairs
Physics). Simulations of 41 ion pairs (box 2), and of 300 ion pairs(box 3). Curves obtained with other AMBER models are given in(box 3). Curves obtained with other AMBER models are given in
Supporting Information
Figure S5.
2""
Supporting Information
Figure S5.

with similar findings in the literature.12,13,16 Even thoughwith similar findings in the literature.12,13,16 Even thoughquantitative coordination numbers may change, the principal
quantitative coordination
numbers may change, the principal
0""
qualitative feature, namely a strong preference for C22-H22‚‚‚Cl
qualitative feature, 2""
namelya strongC -H
4""
6"" box8""preference
10""Thus,
12""for14""16""‚‚‚Cl
bonding, is not affected by thesize.
theanalysisofbonding, is not affected by the box size. Thus, the analysis of
this interaction discussed above should be generally applicable.
this interaction discussed above should be generally applicable.
The overall insensitivity of these short-range interactions toThe overall insensitivityof these short-range interactions to RDF a
the box size
has 4Z
alsoEFP2-MD
been noted inG>bd_`eg^
the other recent DFT-based
the box size has also been noted in the other recent DFT-based
12MD study of Del Pópolo
et al. on25
39 the same system.12 They
They
MD study ofDel Pópolo
et al. on thesame system.
YA)
xCPMD
c/M\ZBL{7SS$
considered a very small box with 8 ion pairs simulated for aconsidered a very small box with 8 ion pairs simulated for a
total time of about 39 ps (sixtrajectories of 6-7ps), andhit;cPRKU
R aa
total time ofg(R)x.L{
about 39 ps (sixtrajectories of 6-7ps), andlarger box of 24 ion pairs simulated for 3.5 ps. Despite somelarger box of 24 ion pairs simulated for 3.5 ps. Despite someinconsistencies concerning structure and energetics of theinconsistencies concerning structure and energetics of theRDF
EFP2-MDRDF
EFP2-MD
RDF
RDF

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Cl- : Br- :-I = 1.4 : 1.2 : 1.0

4

RHF/aug-cc-pVDZ or(DK3-)cc-pVDZ

EFP2

EFP2
4

X--X-RDF

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EFP2

EFP2