2001, Soetens, Molecular Dynamics Simulation and X-ray Diffraction Studies of Ethylene Carbonate,...

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journal of

M O L E C U L A R

LIQUI S

E L S E V I E R

Journal of M olecular Liquids 92 (2001) 201-216

www.elsevier.nl/locate/molliq

M o l e c u l a r D y n a m i c s s i m u l a t i o n a n d X - r a y

d i ff ra c ti on s t u d i e s o f e t h y l e n e c a r b o n a t e p r o p y l e n e

c a r b o n a t e a n d d i m e t h y l c a r b o n a t e i n l i q u i d p h a s e

J e a n - C h r i s t o p h e S o e t e n s

Laboratoire de Physico-Chimie Moldculaire UMR CNRS-Universitd Bordeaux I n°5803

351 cours de la Libdration 33405 Talence Cedex France

C l a u d e M i l l o t , B e r n a r d M a i g r e t

Laboratoire de Chimie thdorique UMR CNRS-Universitd Henri-Poincard-Nancy I

n ° 7 5 6 5 ,

Boulevard des Aiguillettes BP 239 5~506 Vandoeuvre-lds-Nancy Cedex France

I m r e B a k 6

Central Research Institute for Chemistry Hungarian Academy of Sciences

H-1025 Budapest Hungary

M o l e c u l a r D y n a m i c s s i m u l a t i o n s o f p u r e e t h y l e n e c a r b o n a t e , p r o p y l e n e c a r b o n a t e a n d d i m e t h y l

c a r b o n a t e h a v e b e e n c a r r i e d o u t a t d i f f er e n t t e m p e r a t u r e s i n t h e l i q u id p h a s e . T h e a l l a t o m

O P L S p a r a m e t e r s a r e u s e d t o d e s c r i b e v a n d e r W a a i s i n t e r a c ti o n s a n d t h e a t o m i c c h a r g e s a r e

ob ta ined f rom a b in i t i o 6 -31G** SC F ca l cu la t ion s . For t he f l ex ib le mod e l s , va r ious fo r ce f ie lds

h a v e b e e n t e s t e d a n d c f f g l h a s b e e n c h o s e n t o d e s c r i b e i n t r a m o l e c u l a r i n te r a c t i o n s . T h e r m o d y -

n a m i c a l a n d d y n a m i c a l p r o p e r t i e s a r e r e p o r t e d a n d a r e a s o n a b l e a g r e e m e n t w i t h t h e a v a i l a b l e

e x p e r i m e n t a l d a t a i s o b se r v e d . S i m u l a t e d s t r u c t u r e o f e t h y l e n e c a r b o n a t e a n d p r o p y l e n e ca r -

b o n a t e a t 3 2 3 a n d 4 73 K a r e c o m p a r e d w i t h t h e e x p e r i m e n t a l o n e d e t e r m i n e d a t t h e s a m e

t e m p e r a t u r e s u s in g X - r a y d i ff ra c ti o n e x p e r im e n t .

© 2001 E lsevier Science B.V. A ll fights reserved.

1 I n t r o d u c t i o n

E t h y le n e ca r b o n a t e ( E C : 1 , 3 - d i o x o l a n e - 2 - o n e ) , p r o p y l en e c a r b o n a t e ( P C : 4 - m e t h y l -

- 1 , 3 - d i o x o l a n e - 2 - o n e ) a n d d im e t h y l c a r b o n a t e ( D M C ) ( f i gu re 1 ) a r e t h r ee m o le c u le s

o f g r e a t t e c h n o l o g i c a l i m p o r t a n c e b e c a u s e o f t h e i r u s e a s p o l a r a p r o t i c s o l v e n t s i n t h e

e l e c t r o l y t e o f l i t h i u m s e c o n d a r y b a t t e r i e s . S o m e p h y s i c a l p r o p e r t i e s o f t h e s e c o m p o u n d s

a r e g i v e n i n t a b l e 1 . E x p e r i m e n t a l l y , i t i s k n o w n t h a t m i x t u r e s E C / L i C I O 4 o r E C / L i B F 4

a l lo w e ff ic ie n t r e v e r s i b i li t y p r o p e r t i e s . I t h a s a l s o b ee n o b s e r v e d t h a t m i x i n g E C a n d P C

i n t h e e l e c t r o l y t e im p r o v e s t h e b a t t e r y c y c l a b i l i t y [ 1 ]. O f c o ur s e, t h e n u m e r o u s p h y s i c a l

a n d c h e m i c a l p r o c e ss e s o c c u r i n g in b a t t e r i e s a r e q u i t e c o m p l i c a t e d a n d i t d o e s n o t s e e m

p o s s ib l e t o s t u d y a l l o f t h e m s i m u lt a n e ou s l y. F o r e x a m p l e , t h e c h a r g e - d i s c h a r g e

0167-7322/01/ - see front matter © 2001 Elsevier Science B.V. A ll fights reserved.

PII S0167-7322(01) 00192-1


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1 1

[

oS \o

\ \

H 1 ~ H H a H 3

H~ H3 H ~ C ~ . - . . H 5

H4 H

H5

H i

Figu re 1 : S t ruc tu r e o f EC ( l ef t ), PC (midd l e ) and D M C ( r igh t ) mo lecu l e s and de f in i ti on

o f t h e a t o m i c l a b e l s u s e d in t h e r e s t o f t h e p a p e r . D M C i s p r e s en t e d i n a t r a n s - t r a n s

con fo rma t ion .

cyc le involves d isso lu t ion and depo s i t ion o f l i th ium thro ug h a f ilm (obta in ed f i om re-

duc t i on o f t he so lven t ) a cco rd ing t o a dend r i t i c g rowth . Th e fu ll und e r s t and ing o f t he

e l ec t rochemica l p roces s occu r ing i n t he ba t t e ry wou ld r equ i r e t o s t udy t he anode , t he

ca thode , t he e l ec t ro ly t e and t he i r i n t e r f ace s . I n t h i s work , we focus on a l e s s amb i t i ous

t a sk . We desc r ibe an e f fo r t t o ge t r e a sonab l e i n t e r ac t i on po t en t i a l s f o r t he t h r ee ca rbon -

a t e s , and p r e sen t expe r im en ta l s tud i e s o f t he l iqu id s t ruc tu r e ( fo r EC and P C) ob t a ined

b y X - r a y d i ff ra c ti o n . M o l e c u la r D y n a m i c s ( M D ) s i m u l a t i o n s o f L i B F4 i n E C , P C a n d

DMC have been r epo r t ed e l s ewhe re [2 ] . Ab in i t i o c a l cu l a t i ons on t he monomers a r e u sed

to l oca t e t he s t a t i ona ry po in t s on t he po t en t i a l ene rgy su r f ace , t o de t e rmine t he i r r e l a t i ve

ene rg ie s and t o f it pa r t i a l a t om ic cha rges. Th e o the r in t e r ac t i on po t en t i a l pa r am e te r s

(Lenna rd - Jones ) and i n t r amo lecu l a r f o rce f ie ld s a r e t aken f rom the l i t e r a tu r e .

In s ec ti on 2 , we r epo r t t he r e su l ts o f X - r a y d i f f rac t i on expe r ime n t s . I n s ec t ion 3 , we f ir s t

p r e sen t t he r e su l t s o f ab i n i t io c a l cu l a t ions on t he m onom ers and we desc r ibe t he i n t e r -

a n d i n t r a m o l e c u l a r p o t e n t i a l s , t h e n t h e r m o d y n a m i c a l a n d d y n a m i c a l r e s u l t s o b t a i n e d

f rom MD s imu la t i ons a r e p r e sen t ed . F ina l l y i n s ec t ion 4 , s imu la t i ons r e su l t s conce rn ing

t h e s t r u c t u r e a r e p r e s e n t e d a n d c o m p a r e d w i t h e x p e r i m e n t a l r e s u l t s o b t a i n e d b y X - r a y

d i f f r ac t i on fo r EC and PC.

Tab le 1 : Som e mo lecu l a r and l i qu id phase p ro pe r t i e s o f t he t h r ee so lven t s A t em pe r a tu r e

dep end ance of the l iqu id den s i ty for EC and PC can be foun d in re fe rences [3] and [4] .

D a t a f rom R e f [5] excep t ( a ) : R e f [6] ( vapo r i za t i on en tha lp ie s a t t he bo i l ing po in t ) and

(b ) : Re f [7 ] ( vapo r i za t i on en tha lp i e s a t 293 K) .

E C P C D M C

M /g.m o1-1 88.06 102.09 90.08

m p /° C 36 .4 -48.8 0 .5

b p /° C 248.0 242.0 90.5

p /g . cm -3 1 .3214 39 °C) 1.204 7 2o °C) 1.0694 (20 °C)

eo 89.78 (40 °C ) 66.14 (20 °C ) 3.09 (25 °C )

A H va p/k ca l.m o1 -1 12.2 (a) 11.9 (a) 8.9 (b)


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2 E x p e r i m e n t a l X r a y d i ff ra c ti on s t u d i e s r e s u lt s

A n a l y s i s p r o c e d u r e s

T h e X - r a y d i f f ra c t i o n e x p e r i m e n t s w e r e c a r ri e d o u t a t 3 2 3 K w i t h a S e if e rt 0 - 0 d i ff ra c -

t o m e t e r u s i n g t r a n s m i s s i o n g e o m e t r y w i t h M o K a r a d i a t i o n (A = 0 .7 1 1 fl,). T h e o b s e r v e d

r a n g e o f s c a t t e r i n g a n g l e ( 2 0) w a s b e t w e e n 0 . 6 ° a n d 1 1 0 ° , w h i c h c o r r e s p o n d s t o a Q r a n g e

f r o m 0 . 1 / ~ - 1 t o 1 4. 5 ~ - 1 , w h e r e Q is t h e s c a t t e r i n g v a r i a b l e (Q - - ~ s i n 0 ) . T i m e s r e q u ir e d

t o a c c u m u l a t e 1 2 00 0 0 c o u n t s a t e a c h a n g l e w e r e re g i s te r e d . T h e o b s e r v e d i n t e n s i t ie s w e r e

c o r r e c t e d fo r b a c k g r o u n d , a b s o r p t i o n , i n c o h e r e n t s c a t t e r i n g a n d a n o m a l o u s s c a t t e r i n g u s -

i n g t h e s t a n d a r d m e t h o d s , a n d n o r m a l i z e d t o t h e s c a t t e r i n g o f i n d i v i d u a l a t o m s u s i n g t h e

K r o g h - M o e m e t h o d [ 8] . D e t a i ls o f t h e d i f f ra c t o m e t e r a n d t h e g e n e r a l m e t h o d o f m e a s u r e -

m e n t a n d d a t a t r e a t m e n t w e r e d e s c r i b e d e ls e w h e r e [9 , 1 0]. T h e e x p e r i m e n t a l s t r u c t u r e

f u n c t i o n s I ( Q ) a r e d e f i n e d a s :

I (Q ) = I a ~ ( Q ) - ~ ~ x ~ f ] ( Q ) / ( x~ f~ ( Q )) 2 (1 )

1

w h e r e I ab s ( Q ) i s t h e n o r m a l i z e d i n t e n s i t y , x ~ is t h e a t o m i c f i 'a c t i o n a n d f a ( Q ) i s t h e

s c a t t e r i n g l e n g t h o f a t o m t y p e a . T h e e x p e r i m e n t a l t o t a l p a i r c o r r e l a t i o n f u n c ti o n G ( r )

w a s c a l c u l a te d a s a F o u r i e r t r a n s f o r m o f t h e Q . I ( Q ) f u n c t i o n

G ( I ' ) = 1 + 2 - ~ p r Q I ( Q ) s i n ( Q r ) d r ( 2)

w h e r e p i s t h e m o l e c u l a r n u m b e r d e n s it y . T h e e x p e r i m e n t a l s t r u c t u r e f u n c t i o n s a n d t h e

r e l a t e d p a i r c o r r e l a t i o n f u n c t i o n s o f E C a n d P C a r e sh o w n i n f ig u r e s 2 a n d 3 r e s p e c t i v e l y .

S t r u c t u r e a n a l y s i s a n d r e s u l t s

I n a t t e m p t s t o r e v e a l t h e s t r u c t u r e o f m o l e c u l a r li q u id s , t h e s t r u c t u r e f u n c t i o n i s o f t en

c o n s i d e r e d a s a s u m o f t h e i n t r a m o l e c u l a r a n d t h e i n t e r m o l e c u l a r t e r m s .

I (Q ) = I in t ra(Q) + I in ter (Q) (3)

T h e I i~ t ra ( Q ) c a n b e e x p r e s s e d i n t h e f o l l o w i n g f o r m

I i~ t ra (Q ) = i ~ x i x f i (Q ) f j (Q ) s in (Q r i j ) l ~ O 2

Q r ij e x p ( - 2 ~ - ' ) / (~ -~ x i f i ( Q ) ) 2

4 )

w h e r e r ij i s t h e d i s t a n c e b e t w e e n a t o m s i a n d j i n t h e m o l e c u l e a n d lij c h a r a c t e r i z e s i t s

t h e r m a l f l u c t u a t i o n . I n o u r a n a l y s i s , w e a s s u m e d t h a t Iin te r(Q ) v a n i s h e s a t 6 h - I a n d

t h e v a l u e s o f r ij a n d lij a r e d e t e r m i n e d t o f i t t h e f u n c t i o n o f I in t ra ( Q ) t o t h e e x p e r i m e n t a l

s t r u c t u r e f u n c t i o n i n t h e r a n g e f r o m 6 / ~ - 1 t o 1 4. 5 ~ - 1 .

T h e s h a p e o f t h e t h e o r e t i c a l Q . I ( Q ) f u n c t i o n s o b t a i n e d f r o m t h e b e s t f i t, w i th t h e e x p e r -

i m e n t a l f u n c t i o n s a r e s h o w n i n fi g u re 2. A s t h e f i rs t s t e p t h e s t r u c t u r a l p a r a m e t e r s f o r


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.0 i i i i i

6.0 -/ ' , ,

5.0 ;

4 .0

3 .0

0 ~ 2.0 / ' , , , , ,

1 o

0.0

-1 .0

-2 .0

0.0 2.0 4.0 6.0 8.0 10.0 12.0 14.0

Q (A -1)

F i g u r e 2: E x p e r i m e n t a l t o t a l s t r u c t u r e f u n c t i o n s s o li d l in e ) f o r E C a n d P C o b t a i n e d f r o m

X - r a y d i f f ra c t i o n e x p e r i m e n t a t 3 2 3 K . I n d a s h e d l in e , f i tt e d s t r u c t u r e f u n c t i o n s in t h e

r a n g e f r o m 6 t o 1 4.5 /~ - 1 t o d e t e r m in e rij a n d lij p a r a m e te r s .

5.0

4.0

3.0

2 .0

1.0

0 .0

E C

i | i

2.0 4 .0 6 .0

P C

0.0 8.0 10.0

r (A)

F i g u r e 3: E x p e r i m e n t a l t o t a l p a i r c o r r e la t i o n f u n c t i o n s f o r E C a n d P C o b t a i n e d f r o m

X - r a y d i ff r ac t io n e x p e ri m e n t a t 3 2 3 K .


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205

t h e s k e l e t o n o f E C w e r e r e fi n e d u s in g t h e l e a s t s q u a r e s m e t h o d . T h e f in a l p a r a m e t e r s a r e

s h o w n i n t a b l e 2 b y c o m p a r i n g w i t h t h o s e f ro m a b i n i t i o c a l c u l a t i o n s a n d X - r a y d i ff ra c -

t i o n r e s u l ts . T h e a g r e e m e n t i s f a i r l y g o o d . I n t h e s e c o n d s t e p f o r t h e P C w e f i x ed t h e

p a r a m e t e r s c o m m o n t o E C a n d P C a n d f i t t e d th e n e w r ij a n d lij p a r a m e t e r s i n v o lv i n g t h e

m e t h y l g r o u p . T h e p a r a m e t e r s a r e s h o w n i n t a b l e 3 .

T a b l e 2 : I n t r a m o l e c u l a r d i s t a n c e s r ii ( /~ ) a n d t h e r m a l f l u c t u a t i o n s lij (A ) i n E C .

a b i n it io X - r a y

rl) rij lij

C1 - O1 1 .190 1 .20 0 .09

C1 - 02 1 .362 1 .34 0 .12

02 - C2 1 .428 1 .46 0 .13

C2 - C2 1 .520 1 .52 0 .11

O1 - 02 2 .23 2 .18 0 .10

O1 - C2 3 .28 3 .42 0 .20

C2 - O3 2 .29 2 .37 0 .17

C1 - C2 2 .25 2 .28 0 .16

O 2 - O s 2 .1 8 2 . 19 0 .1 5

T a b l e 3: I n t r a m o l e c u l a r d i s t a n c e s r ij ( /k ) a n d t h e r m a l f l u c t u a t i o n s i ij ( A ) i n P C .

a b i n it io X - r a y

rq rij lij

C4 - 03 2 .41 2 .49 0 .21

C4 - C2 2 .57 2 .48 0 .24

C4 - O2 3 .58 3 .57 0 .28

C4 - C1 3 .48 3 .37 0 .25

C4 - O1 4 .53 4 .53 0 .21

3 C o m p u t e r s i m u l a t i o n s

3 1 D e s c r i p t i o n o f t h e p o t e n t i a l e n e r g y f u n c t io n s

A b i n i t i o c a l c u l a t i o n s o n m o n o m e r s

H i g h l e v e l a b i n i t i o c a l c u l a t i o n s h a v e b e e n d o n e a t M P 2 / 6 - 3 1 1 G * * l e v e l f o r E C a n d P C

a n d M P 2 / 6 - 3 1 G * * / / R H F / 6 - 3 1 G * * l ev e l f or D M C . T h e m o s t i n t e r e s t in g s t ru c t u r a l p r o p -

e r t y o f E C a n d P C m o l e c u l es i s t h e i m p o r t a n c e o f t h e n o n - p l a n a r i t y o f t h e i r ri ng . E x -

p e r i m e n t a l l y , o n l y t h e s t r u c t u r e o f E C m o l e c u l e h a s b e e n d e t e r m i n e d i n c r y s t a l p h a s e .

M a t i a s e t a l [ 1 1 ] a n d B r o w n [ 1 2] r e p o r t a C 2 s y m m e t r y f or E C w i t h a d i h e d r a l a n g l e

0 2 - C 2 - C a - O ~ o f 2 4. 8 ° a n d 2 7.1 ° r e s p e c t i v e l y . A n o t h e r e x p e r i m e n t a l r e s u l t f i o m

A l o n s o e t a l [ 13 ] p r e d i c t a r i n g i n v e rs i o n o f E C t h r o u g h t h e p l a n a r r i n g o f C 2 , s y m m e t r y

w i t h a b a r r i e r o f 0 . 6 7 k ca l .m o 1 - 1 . F r o m o u r a b i n i t i o c a l c u l a t i o n , t h e C 2 c o n f o r m e r w i t h

t h e d i h e d r a l a n g l e e q u a l t o 2 9 .5 ° is m o r e s t a b l e t h a n t h e C 2~ o n e b y 1 .1 8 k c a l . m o l - k


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No experimental da ta are available for the structure of PC. Due to the presence of the

methyl group, the two twisted minima corresponding to the ring inversion are not anymore

exactly equivalent, nevertheless our ab initio calculations predict a very small energy dif-

ference of 0.04 kcal.mo1-1. The barrier height for ring inversion is equal to 1.29 kcal.mol-1

at this level of theory.

The potential surface of DMC presents two impor tant minima, the tran s- tr ans con-

former with C2v symmetry (figure 1) which is the lowest energy structure and the

trans-cis conformer with Cs symmetry, which can be obtained from the previous one

by rotating one methyl 180° around the C1-O3 (or C2-O2) bond. We found at ab ini-

tio MP2/6-31G* *//RHF /6-31G ** level that the trans -ci s conformer is 3.15 kcal.mol -I

higher in energy than the trans-trans conformer, and the barrier energy height between

both conformers is 10.33 kcal.mo1-1. All these results are gathered in tables 4- 6.

Table 4: Some geometrical and energetical parameters of EC molecule in the minimum

energy structure obtained with different force fields, ab initio MP2/6-311G** calculation

and comparison with experimental results. AE is the barrier height from the minimun

energy structure to the planar st ructure, a Ref. [11], b Ref. [13]

EC

AMBER CVFF CFF91 ab initio exp.

bonds/A

angles/°

dihedral/°

O,-C1 1.227 1 . 2 2 9 1 . 1 9 4 1.190 1.203 *

C1-O2 1.368 1. 38 1 1. 37 2 1. 3 62 1.342

Cl-O3 1.368 1.3 81 1. 37 2 1. 36 2 1.342

02-C2 1.428 1.427 1 .4 22 1 . 4 2 8 1.457

O3-C3 1.428 1.427 1. 42 2 1 . 4 2 8 1.457

C2-Ca 1.517 1. 51 0 1.517 1 . 5 2 0 1.522

O1-Cl-O2 124.0 12 4. 4 12 2. 8 12 4 .9 124.2

O~-C1-O3 112.0 11 1. 2 11 4. 4 11 0 .2 111.7

C1-O2-C2 105.1 10 7. 8 10 4. 9 10 8. 3 108.7

C1-03-C3 105.1 1 0 7 . 8 1 0 4 . 9 108.3 108.7a

02-C2-C3 101.2 1 0 4 . 4 104.0 102.1 102.2 a

O2-C2-C3-Oa 38.5 21.0 28.4 29.5 24.8

Cl-O2-C2-C3 -31 .4 -17 .2 -2 2.7 -24 .9 -21.3

C1 03 C3 C 2

-31.4 -17.2 -22.7 -24.9 -21.3

02-C1-03-Ca 12.9 7.0 9.4 10.3 9.0

AE/kcal.mo1-1 4.72 0.27 0.57 1.18 0.67 b


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Table 5: Some geometrical and energetical parameters of PC molecule in the minimum

energy structure obtained with different force fields, ab initio MP2/6-311G** calculation

and c©m,~ai~so~ w'~h~ ex, ei)men~a~ resu~s, ~ ~s ~)e ~DaH]e~)o~g:~ ~n)r~ ~o~ zi)~ )m v~

energy structure to the planar structure. AE' is the energy difference between both

minima related by the ring inversion.

bonds/A

a n g l e s °

dihedral/°

PC

AMBER CVFF CFF91 ab initio

O~-C~ 1.227 1 . 2 2 9 1.194 1.190

C~-O~ 1.368 1. 38 1 1 . 37 3 1.362

C~-O3 1.368 1. 38 2 1 .3 71 1.361

O2-C~ 1.427 1.430 1 . 4 2 2 1.427

O~-C3 1.429 1. 43 6 1 .4 29 1.435

C2-Ca 1.519 1 . 5 1 2 1.517 1.521

Cs-C4 1.531 1. 52 4 1. 54 0 1.509

O~-C1-O2 123.9 1 2 4 . 5 1 2 2 . 9 124.8

O2-C~-O3 112.0 1 11 . 1 1 1 4 . 2 110.2

C~-O2-C2 105.1 1 0 7 . 6 104.0 108.2

C~-O~-C3 105.3 1 0 7 . 6 104.7 108.8

O~-C~-C3 101.3 1 0 4 . 2 103.7 102.9

C~-C3-C4 116.5 1 1 5 . 6 1 1 3 . 9 115.3

O~-C2-Cs-Oa -38 .5 -24.1 32.9 28.3

Cl O2 C2 C3 31.6 19.9 -26. 8 -23. 7

C~-O3-Cz-C2 31.3 19 .8 -25.8 -24 .1

O2-Ct-O3-Ca -12. 8 -8 .2 11.4 9.8

AE/kcal.mol -~ 5.04 0.71 1.49 1.29

AE'/kcal.mol-~ 1.00 - 0.48 0.04

n t r a m o l e c u l a r

potent ia l

literature: A~I B~I IS] , C~I~yII6 and CFF9 II I7 i8]. Each force field has been tested

by optimizing the par ticular structures discussed in part 2.1. The results for optimum

Conce~i~g EC, ¢b,e A~ ,~l, , f~c ¢ ii~{d p~edi~'~s ~ ~oo ~is~ed molecule, with a dihedral

angle O2 - C2 - C3 - O3 of 38.5 degrees versus 24.8 degrees from experiment and an im-

portant energy difference with the planar structure, 4.72 kcal.mo1-1 to be compared with

the experimental value of 0,67 kcakmo]-l. With CvF~', the same dihedral ~ngle is 21.0 de-

grees and ~be b~rr}ere~ergy rson}y {).27 kcaLmo~ ~. C~'1~31 seems to be the more accurate

force field, predicting a dihedral angle 02 - C2 - C3 - 03 equal to 28.4 degrees and an

energy difference between the C2 structure and the planar structure equal 0.57 kcal.mol -~.


8/16

208

T a b l e 6: G e o m e t r i c a l a n d e n e r g e t i c a l p a r a m e t e r s o f t h e D M C m o l e c u l e i n t h e l o w e st

e n e r g y s t r u c t u r e ( t r a n s - t r a n s o f C 2~ s y m m e t r y ) o b t a i n e d w i t h v a r i o u s fo r c e f ie l d s, a b

i n i t io ( M P 2 / 6 - 3 1 G * * / / R H F / 6 - 3 1 G * * ) c a l c u l a t io n s a n d e x p e r i m e n t a l r e s u lt s . A E i s t h e

e n e rg y b a r r i e r fr o m t h e t r a n s - t r a n s g l o b a l m i n i m u m t o t h e t r a n s - c i s m i n i m u m a l o n g th e

r o t a t i o n o f t h e d i h e d r a l a n g l e C2 - 0 2 - C l - O 3. A E ' is t h e e n e r g y d i ff e r e n ce b e t w e e n

t h e t r a n s - t r a n s a n d t r a n s - c i s m i n i m a . ~ R e f . [1 4].

D M C

A M B E R C V F F C F F 9 1 a b i n i t io e x p . ~

b o n d / A

a n g l e s / °

O~-C~ 1.234 1 .240 1 .206 1 .190 1 .203

C~-O2 1.374 1 .380 1 .358 1 .313 1 .443

O~-C2 1 .426 1 .422 1 .435 1 .417 1 .423

C~-H~ 1.090 1 .105 1 .098 1 .079 1 .100

C2-H~ 1.093 1 .107 1 .099 1 .081 1 .100

O~-C~-O~ 122.8 125.1 124 .2 125 .4 -

02 -C ~-0 3 114 .4 109 .9 111 .6 109 .2 107 .0

C~-O~-Cu 113.8 118.8 117.2 116.4 114.5

O2-C2-H~ 108.3 110.4 10 6.2 105.6 111.0

O~-C~-H~ 111.3 111.8 1 11.5 110.6 111.0

A E / k c a l . m o 1 - 1 - - 8 . 6 6 1 0 .3 3

A E ' / k e a l . m o l - ~ 2 .2 2 3 .4 7 3 .3 2 3 .1 5

F o r t h e P C m o l e c u le , t h e A M B E R a n d C V F F f o rc e fi e ld s f a il t o r e p r o d u c e t h e g e o m e t r y

o f t h e m i n i m u m e n e r g y s t r u c t u r e a n d C v F F p r e d i c t s o n l y o n e m i n i m u m . A s f o r E C ,

t ~ b l e 5 ) o f 0 . 48 k c e .l .m o l ~ , e .n e n e r g y b ~ r r i e ~ f~ o m t h e e . b s o lu t e m i n i m a t o t h e p ~ a n a r

s t r~ c t cc r e o f L 4 9 k c a L m a l - ~ a a d a d i he d ~ a~ a a g l e O ~ - C ~ - C ¢ - 0 ¢ o f ~ . ~ d e ~ r e e s I o

b e ~ p a z v d w ~ t b t l~ e ~ b ~n~t~o

p r v d ~ c t i o n s , ¢ ff } . 2 9 k c a I. rr ~ o } - r

~ n d 2 8 . 3 d e g r e e s '

r e s p e c t ? r e l y .

G e o m e t r y o p t i m i z a t i o n o f t h e D M C m o l e c u l e u s i n g t h e t h r e e f o rc e fi e ld s l e a d s to t h e

t r a n s - t r a n s c o n f or m e r a s t h e g lo b a l m i n i m u m . O n l y C F F 9 1 f i n ds t h e t r a n s - c i s c on -

f o r m e r t o b e a l s o a m i n i m u m . M o r e o v e r , a s c a n b e s e e n i n f i g u re 4 , t h i s f or c e f ie ld

r e p r o d u c e s r e a s o n a b l y w e ll t h e a b i n i t i o e n e r g y v a r ia t i o n a s s o c i a t e d w i th t h e t r a n s - t r a n s

t h e b e s t t h e s t r u c t u r a l a n d e n e r g e t i c a l f e a t u r e s o f t h e t h r e e m o l e c u l e s , t h is f o r c e f ie ld h a s

b e e n c h o s en t o b e u s e d i n M o l e c u l a r D y n a m i c s s i m u l a t i o n s

T o e x a m i n e in m o r e d e t a i l s t h e r i n g i nv e r si o n p r o c e s s in E C a n d P C , w e h a v e p e r f o r m e d

4~..rz .?/2 , z,~ ~.f.F2~m[d ~Jmz~ /Jr. z a~ ,r~,~,~t~.~~ ~.z ..P~ ¢'~¢~J~d~ ~ ~:P,~4(~@ ~. ~u ~,h~e~ ae~p o f

Q . 3 c a d e k e C e ~ ' {~ ~ a c o e d ¢ ( 4 . T b : e d a g ~c ¢~ ¢c s( ac¢ ~ . ~ h e d e s c r i b e d (~ y ~ ~ ~ ( 9 ~ ¢ ~ e r i n g

c o o r d i n a t e s w h i c h c h a r ac t e r i z e s t h e d e v i a t i o n o f a t o m i c p o s i t i o n s w i t h r e s p e c t t o a m e a n

p l a n e [ 1 9 , 2 0 ] . A c c o r d i n g t o t h i s f o r m a l i s m , t h e g e o m e t r y o f a f i v e - m e m b e r e d r i n g is


9/16

209

v

[.r.)

11

10

9

8

7

6

5

4

3

2

÷

i I I i I I I i i i

0 20 40 60 80 100 120 140 160 180

Dihedral angle C2-O2-C1-O1 degrees )

Figure 4: Rota tiona l energy barri er of DMC vs. dihedral angle C2 - O2 - Ct - O1. Solid

line : CFF91 force field; + : ab ini tio MP2/6-31G**/ /RHF /6-31G** results.

• , . , . , ; . . . . : . . . . . . . . . . . : . . - , - " , . , , . : . . ,

. . \ ~ • . . . . , , . / / :

, ' : ' l - * - ' - • ' . . : '

. . : . . . . / . ; . . . . - - . . . . . . . . .

: : , . . . : , , ~ , ,

• 5 f < : ; - ' . - : - ' : N : . ~ .

, . , . g . , , : , ' ~ , , , , ; ' , ¢ . ~ ,

• .~..~,:,., .,,,;*,~ ;

I I I

- 0 .10 0 .00 0 .10

q . c o s p h i )

• . . ', . ~' , ': ' , . * , : * . t 7

~ ' i ' . . . . / /

J / / , , ; , , , , , ~ . ~ '. . .,

. : . . / . - . : - ~ . .

- . - . . .

- ~

. . ' .

, : . ~ i : ~ % ' , ' . ' .

, , ~ . ¢ . ~ ,

,*...'/;

. . . . ~ . . ~ \ * . ..

: / . / , ' : ' , " " , ; : ' d " : ;

• .~t ', ,:,,.:/.Z

I

- 0 .20 - 0 .10 0 .00 0 .10 0 .20

q . c o s p h i )

0 . 5 0

0 . 4 0

0 . 3 0

0 . 2 0

0 . 1 0

0 .0 0 q . s i n p h i )

-0 .10

- 0 .20

- 0 .30

- 0 .40

0 .20

0 . 5 0

0 . 4 0

0 . 3 0

0 . 2 0

0 . 1 0

00000q. s in ph i )

-0 .20

-0 .30

- 0 .40

Figure 5: Prob abil ity dist ribut ion maps of puckering coordinates for EC top) and PC

bott om) obta ine d from MD simulat ions of one molecule at 323 K usi ng the CFF91 force

field.


10/16

210

d e s c r ib e d b y j u s t o n e a m p l i t u d e q a n d o n e p h a s e c o o r d i n a t e ¢ . F r o m t h e M D s i m u l a ti o n s ,

w e h a v e c o m p u t e d t h e d i s t r i b u t i o n f u n c t i o n q , ¢ ) a n d t h e t w o i so d e n s i ty m a p s a r e gi v en

in fi g u r e 5 in a r e p r e s e n t a t i o n q . s i n ¢ ) vs . q . c o s ¢ ) . T h e s e m a p s c l e a rl y s h o w t h a t E C a n d

P C a r e n o t p s e u d o r o t a t o r y m o l e c u l e s , a n d u n d e r g o t h e r i n g i n v e r s i o n t h r o u g h a p l a n a r

o r v e r y n e a r l y p l a n a r f o r P C ) r i n g s t r u c t u r e . I n t h is f ig u re , t h e t w o s y m m e t r i c a l m i n i m a

f o r E C a t t h e c o o r d in a t e s 0 , + 0 .2 7) c o r r e s p o n d t o q = 0 .2 7 A a n d ¢ = : t: 9 0 d e g r e e s a n d

t h e c o n f o r m e r w i t h p l a n a r r i n g is a t t h e c o o r d i n a t e s 0 ,0 ). F o r P C , t h e a b s o l u t e m i n i m a

is a t t h e c o o r d i n a t e 0 , - 0 . 3 1 ) w h i c h c o r r e s p o n d s t o q = - 0 . 3 1 A a n d ¢ = 8 9 d e g re e s.

I n t e r m o l e c u l a r

p ot e n t i l

T h e i n t e r a ct i o n e n e r g y m o d e l c o n si st s o f t h e L e n n a r d - J o n e s a n d c h a r g e - c h a r g e e le c-

t r o s t a t i c i n t e r a c t i o n . T h e t o t a l i n t e r a c t i o n e n e r g y o f t h e s y s t e m i s w r i t t e n a s a s u m o f

i n t e r a c t io n E q . 5 ) b e t w e e n a t o m s a o n m o l e c u le I a n d a t o m s / 3 o n m o l e c u l e J w h i c h a r e

s e p a r a t e d b y t h e d i s t a n c e ra ~ , w i th g e o m e t r i c m ix in g r u l e s E q . 6 )

E _ z (

5)

6)

~ = ~ a s , e ~ ,Z =

T h e v a l u es f o r a a n d e a r e t a k e n f r o m C a r l s o n e t a l . [ 21 ]. T h e a to m ic c h a r g e s h a v e

b e e n o b t a in e d f r o m a b i n i t io 6 - 3 1G * * c a l c u l a t i o n , b y f i t t i n g t h e m o le c u l a r e l e c t r o s t a t i c

p o t e n t i a l o f t h e l o w e s t e n e r g y s t r u c t u r e u s i n g t h e p r o g r a m G R I D [2 2 ]. T h e d i p o l e m o m e n t s

r e c a l c u l a t e d f r o m th e c h a r g e d i s t r i b u t i o n s a r e 6 .0 1 , 6 . 1 5 , 0 . 2 8 a n d 4 .1 1 d e b y e f o r E C , P C ,

t r a n s - t r a n s D M C a n d t r a n s - c i s D M C r es p ec ti ve ly . F o r E C a n d P C , t h es e va lu e s a r e

l a r g e r t h a n t h e e x p e r i m e n t a l o n e s m e a s u r e d i n t h e g a s p h a s e [ 1 3] b y a b o u t 0 . 7 d e b y e, b u t

t h e u s e o f a n e n h a n c e d d i p o l e in c o n d e n s e d p h a s e t e n d s t o c o r r e c t t h e a b s e n c e o f e x p li c it

i n d u c t i o n t e r m . T h e i n t e r m o l e c u l a r p o t e n t ia l p a r a m e t e r s a r e g a t h e r e d i n t a b l e 7 .

3 2

M o l e c u l a r D y n a m i c s s i m u l a t i o n s

T h e M D s i m u l a t io n s a r e ca r r ie d o u t i n t h e N E V e n s e m b le . T h e s y s t e m s a r e c o m p o s e d

o f 2 16 m o le c u l e s i n a c u b i c b o x w i th p e r io d i c b o u n d a r y c o n d i t i o n s . F o r l iq u id P C , w e

u s e a r a c e m i c m i x t u r e o f e n a n t i o m e r s . T h e b o n d l e n g t h s a r e k e p t f r o z en u s i n g t h e R a t t l e

a lg o r i th m [ 2 3 ] a n d t h e t im e s t e p i s 1 .0 f s. T h e v a l i d i t y o f t h e s e a p p r o x im a t io n w i th r e-

s p e c t t o t h e f u l l f l ex ib le f o r c e f ie ld s p r e v io u s ly d e s c r ib e d h a v e b e e n c h e c k e d t h r o u g h M D

s im u la t i o n s o n l i q u id E C, a n d n o s i g n i f ic a n t d if f e re n c e s h a v e b e e n o b s e r v e d . T h e i n t e r -

a c t i o n s a re t r u n c a t e d b e y o n d a m o l e c u l a r) c u t - o f f d i s t a n c e e q u a l t o h a l f t h e b o x l e n g t h

a n d l o n g r a n g e d e l e c t r o s t a t i c i n t e r a c t i o n s a r e t a k e n i n to a c c o u n t u s in g t h e r e a c t i o n f i e l d

t e c h n iq u e [ 2 4 , 2 5, 26 ] w i th t h e d i e l e c t r ic c o n s t a n t o f t h e s u r r o u n d in g c o n t i n u u m s e t t o

o c . D a t a a r e c o l l e c t e d d u r in g 7 5 p s f o l l o w in g a n e q u i l i b r a t i o n p e r io d . F o r e a c h t e m p e r a -

tu r e , t h e b o x s i ze is a d ju s t e d t o c o r r e s p o n d t o t h e e x p e r im e n ta l v a lu e o f t h e l i q u id d e n si t y .


11/16

2

Tab le 7 : van de r W aa l s pa r am e te r s an d cha rges o f t he i n t e rm o lecu l a r po t en t i a l f o r EC,

PC and D M C molecu l es . T he l abe l s o f a tom s a r e de fined in f i gu re 1 .

Molecu l e s A tom

a a e c q ~

typ e ( ]~) (kca l .mo1-1) (e )

EC O1 2 .96 0 .210 -0 . 64 52

C1 3.75 0.105 1.0996

02-3 3 .00 0 .170 -0 .4 68 4

C2-3 3.50 0.066 0.0330

H1-4 2.50 0.030 0.1041

P C

O1 2 .96 0 .210 -0 . 63 78

C1 3.75 0.105 1.0489

02 3 .00 0 .170 -0 . 45 09

03 3 .00 0 .170 -0 . 41 20

C2 3 .50 0 .066 -0 . 00 40

C3 3.50 0.066 0.0832

Ca 3 .50 0 .066 -0 .32 64

H~ s 2.50 0.030 0.1165

D M O1 2 .96 0 .210 -0 . 67 74

C1 3.75 0.105 1.0864

02-3 3 .00 0 .170 -0 .4 47 8

C2-3 3 .50 0 .066 -0 .1 56 1

H t-6 2.50 0.030 0.1331

Th e d i ffu s ion coe ff ic i en t is ob t a ined f rom the cen t e r o f mass ve loc i t y au toco r r e l a t i on func -

tion [27].

l f

= ~ < v ( 0 ) . v ( t ) > d t (7 )

Th e o r i en t a t i ona l c o r r e l a t i on times r l and r2 o f t he z an d x ax i s (O l - C~ and C2 - C3

bonds r e spec t i ve ly ) have been co mp u ted f rom an ex ponen t i a l f i t t ing o f t he l ong t ime be -

hav io r o f t he r eo r i en t a t i ona l au toco r r e l a t i on func t i ons P l (u ( 0 ) . u ( t ) ) and P 2 (u (0 ) . u ( t ) ) ,

whe re u ( t ) i s a un i t vec to r a long an ax i s and P I a Legendre po lynomia l .

A l l t he m o lecu l a r dyn am ics r e su l ts a r e p r e sen t ed i n t ab l e s 8 and 9 . Th e t o t a l p o t en t i a ]

e n e r gy c a n b e c o m p a r e d w i t h t h e e x p e r i m e n t a l h e a t o f v a p o r i z a t i o n A H ~ p a t t h e c o rr e -

s p o n d i n g t e m p e r a t u r e . U n f o r t u n a t el y , w e kn o w o n ly t h is p r o p e r t y f o r l iq u id E C a n d P C

a t t he bo i l i ng po in t : t he dens i t i e s o f t he l i qu ids a r e no t known a t t he se t em pe , a tu r e s .

A n a c c u r a t e c o m p a r i s o n b e tw e e n t h e e x p e r i m e n t a l a n d s i m u l a t e d h e a t s o f v a p o r i z a ti o n i s

thus not po ss ib le . At 473 K , we found a pote nt ia l en ergy of 14 .25 and 13 .09 kca l.mo1-1

which co r r e sponds a pp rox im a te ly t o 15 .2 and 14 .0 kcal .mo1-1 fo r t he h ea t o f vapo r i za t i on

a t t h i s t em pe r a tu r e s fo r EC and P C r e spect i vely . A c rude ex t r apo l a t i on ( in t he le as1


12/16

212

s q u a r e s e n s e) o f o u r r e s u lt s t o t h e b o i l in g p o i n t t e m p e r a t u r e s l e a d s to a n e r r o r o n t h e

h e a t o f v a p o r i z a t i o n o f a b o u t 1 0 - 1 5 % .

T o o u r k n o w l e d g e t h e e x p e r i m e n t a l d i f f u s io n c o e f fi c ie n t o f t h e s e l i q u i d c a r b o n a t e h a s

n o t b e e n p u b l i s h e d . A n ' e x p e r i m e n t a l ' e s t i m a t e o f t h e d i f f u s io n c o e f fi c ie n t f o r E C a n d

P C h a v e be e n d e t e r m i n e d f r o m t h e i r e x p e ri m e n t a l v is c o si ti es t h r o u g h t h e W i l k e - C h a n g

fo rmula [28 ] :

D A B - -- - l ' 1 7 1 0 - 6 ( T ) ( ( ~ M B ) l / 2

~ B V ~ : 6 8 )

i n w h i c h D A B is t h e d i f f u s i o n c o e f fi c i e n t o f a s o l u t e A i n a s o l v e n t B ( m 2 . s - 1 ) , M u t h e

m o l e c u l a r m a s s o f t h e s o l v e n t , T t h e t e m p e r a t u r e , # B t h e v i s c o s i t y o f t h e s o l v e n t ( P a . s ) ,

V A t h e m o l e c u l a r v o l u m e o f t h e s o l u t e ( m a . k m o 1 - 1 ) a n d ~b a n a s s o c i a t i o n p a r a m e t e r ( 1. 5 in

o u r c a s e ) . T h i s r e l a t i o n h a s p r o v e d t o b e r e l a t i v e l y p r e c i s e f o r a l a r g e n u m b e r o f s y s t e m s .

B y M D s i m u l a t i o n , w e h a v e f o u n d a d i f f u s i o n c o e f f i c ie n t o f 0 . 7 0 a n d 0 . 5 0 1 0 - 9 m 2 . s - 1 f o r

E C a n d P C r e s p e c ti v e l y , v a l ue s w h i c h a r e in r e a s o n a b l e a g r e e m e n t w i t h t h e e s t i m a t e d

' e x p e r i m e n t a l ' o n e ( 0 .8 0 a n d 0 . 56 1 0 - 9 m 2 . s - 1 ) .

T a b l e 8: R e s u l t s o f t h e m o l e c u l a r d y n a m i c s s i m u l a t i o n s o f l iq u i d E C a n d D M C . < # >

i s t h e a v e r a g e m o l e c u l a r d i p o l e m o m e n t . R e s u l t s l a b e l l e d (a ) h a v e b e e n o b t a i n e d f i 'o m

e q u a t i o n 8 .

E C P C D M C

T / K 3 2 3 .1 5 4 7 3 . 1 5 2 9 8 . 1 5 3 2 3 . 1 5 4 7 3 . 1 5 2 9 8 .1 5

p / g . cm -3 1 .3084 1 .1439 1 .1951 1 .3084 1 .1439 1 .0694

< E pot > / k c a l . m o 1 - 1 - 1 6 . 9 6 - 1 4 . 2 5 - 1 7 . 1 7 - 1 6 . 4 1 - 1 3 . 0 9 - 1 2 . 2 5

< Eel > / k c a i . m o 1 - 1 - 7 . 3 0 - 6 . 3 1 - 6 . 4 3 - 6 . 2 0 - 5 . 1 4 - 3 . 3 7

< E L j > / k c a l . m o l - I - 9 . 6 6 - 7 . 9 4 - 1 0 .7 4 - 1 0 .2 1 - 7 . 9 5 - 8 .8 8

< # > / d e b y e 6 . 0 2 6 . 10 6 . 2 7 6 . 3 0 6 .3 1 1 .2 9

< P r es s ur e > / 1 0 S P a 69 2 - 6 1 5 - 4 8 8 - 5 2 3 - 6 5 9 - 1 6 9

< i d e a l p a r t > 4 0 5 5 26 2 6 9 3 0 8 4 1 3 3 1 3

< v i r ia l p a r t > 286 - 1 1 4 1 - 7 5 8 - 8 3 1 - 1 0 7 2 - 4 8 2

Di f fus ion coef f i c i en t 0 .70 2 .98 0 .50 1 .10 3 .48 1 .43

D /1 0 -9 m2.s -1 0 .80 (a) _ 0 .56 (a) - _ _

%(1)/ps 14.2 2.1 26.2 16.5 2.9

r~(2)/ps 10.2 1.3 10.6 6.2 1.7

% 0) /ps 32 .8 5 .2 60 .2 34 .1 7 .1

~-(2) /ps 14.3 2 .0 21.9 11.9 2 .7


13/16

213

4 Comparisonbetw een experim ental and sim ulated

s ~ r u t u r e s

Some

a t o m - a ~ o m

raffta)

f f t s ~ f tb u ( t o ~ ~ u n c f t o n s a r e p r es en ~ ;e c~ m ~ g u r e

~

Y~e g~ve .'/~ts'~

three fun ction s for each l iquid car bo nat e go~o~ r), go~c~ r) an d gc~c~ r)) , a t 323 and 473

K fo r EC and P C which a re the t empera tu re s used in the expe r imen t s.

g

1.6

1: ~ ~ ~

0.8

0.4

0.0

2.0 4.0 6.0 8.0 10.0 12.0

6 6 i :

.2 ~ ~5 1.2

0.8 ~ 0.8

0.4 0.4

0.0 0.0

2.0 4.0 6.0 8.0 10.0 12.0 2.0 4.0 6,0 8,0 10,0 12,0

1.6

0.8

0.4

0.0

2.0 4.0 6.0 8.0 10.0 12.0

1 6 1 6

1 2 ~ ~ 1 2

0.8 7 ~ 0.8

0.4 0.4

0.0 0.0

2.0 4,0 6.0 8.0 10.0 12.0 2.0 4.0 6.0 8.0 10.0 12.0

1.6

1.2

U

0.8

0.4

0.0

2.0

U

4.0 6.0 8.0 10.0 12.0

1.6

1.2

0.8

0.4

0.0

2.0

1.6

~ 2

0.8

0.4

0.0

4.0 6.0 8.0 10.0 12.0 2.0

4.0 6.0 8.0 10.0 12.0

R ( Angstroms R ( Angstroms R ( Angstroms)

Figure 6: Some in te rmoleeu la r a t om -a to m rad ia l d i s t r ibu t ion func t ions fo r liqu id EC

lef t co lum n) an d PC mid dle colum n) obta ine d a t 323 K solid l ine) and 473 K da .~hed

line) and for l i q u i d D M C r ight column} obta ine d a t 2 9 8 K .

The to ta | in te rmoieca laT s t ruc ture funct ions I in ter (Q/ can be obta ined f rom the MD s im-

u la t i ons a c c o r d i n g ~ o :

r °° 2sin (Q.r )

I i . t ~ , Q ) =

4 r P ] o

r ~ G i . , ~ r ) - 1 ) d r 9 )

of the lpa~fdl ~n~ermd~ecdlar ra~xdI ~lst~ibuOon ]unc~io ns:

a


14/16

214

and w~a is t he ave r age s ca t t e r i ng s t r eng th ove r a l l measu red p o in t s de sc r i bed in t he

ana ly s i s p rocedu re s :

1 (2 -

a~e)f~ Q)f~ Q)

(11)

w~e = -N ~ g . f . Q))2

points

The expe r imen ta l i n t e rmo lecu l a r s t r uc tu r e f unc t i ons have been ob t a ined f rom equa t i ons 3

and 4 and a r e com pared w i th t he ones ca l cu l a t ed f rom the p r e sen t M D s im u la t i on i n f igu re

7 . Th e co r r e spond ing pa i r co r r e la t i on func t i ons a r e shown in f igu re 8 . Th e com par i son

o f t he s imu la t ed and expe r im en ta l i n t e rmo lecu l a r s t r uc tu r e f unc t i ons show a ve ry good

ag reem en t i n t he pos i t i on o f t he p eaks and j u s t an excess o f s t r uc tu r e i s obse rved a round

1.5 A -1.

6.0

5.0

4.0

3.0

,-, 2.0

1.0

• o.o

C,, -1.0

-2.0

-3.0

-4.0

0.0

~ _ _ PC

2.0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 14 .0

Q (A l)

F igu re 7 : T o t a l i n t e rmo lecu l a r s t r uc tu r e f unc t ions fo r l iqu id EC and P C ob t a ined f l'om

molecu l a r dynamics s imu la t i ons ( so l i d l i ne ) a t 323 K and compar i son w i th expe r imen ta l

X - r a y r e s u l t s ( + ) .

2.5

~ . EC

2 . 0 . . . . . . .

1.5 Z

0

0.5

0.0

- 0 . 5 . . . . . .

0 .0 2 .0 4 .0 6 .0 8 .0 1 0 .0 1 2 .0 14 .0

r (A)

F igu re 8 : To t a l i n t e rmo lecu l a r pa i r co r r e l a t i on func t i ons fo r l i qu id EC and PC ob t a ined

f rom molecu l a r dynamics s imu la t i ons ( so l i d l i ne ) a t 323 K and compar i son w i th expe r i -

me n ta l X - r a y r e su l t s ( da shed line) .


15/16

215

C o n c l u s i o n

Thi s w or k de sc ri be s t he m ode l l i ng o f th r ee l i qu i d ca r bona t e s u s i ng Mol ecu l a r D ynam i cs

s i m u l a ti ons and r ea sonab l e si m p l e po t en ti a l s , w h i ch a r e am ong t he m o s t pop u l a r so l ven t s

used i n e l ec t r o ly t e s o f l i th i um ba t t e r ie s , n am e l y e t hy l ene ca r bona t e , p r opy l ene ca r bona t e

and d i m e t hy l c a r bona t e . Th e i n t e r m ol ecu l a r pa r t o f t he i n t e r ac t i on po t en t i a l cons is ts

of Le nnard -Jone s param eters an d ab in i t io poten t ia l der ived charges. T he f l ex ib il i ty of

t he m o l ecu l e s , pa r t i cu l a r l y i m por t an t f o r t he d i m e t hy l c a r bona t e i s t ak i ng i n t o accoun t

t h r ough t he u se o f t he i n t r am ol ecu l a r pa r t o f t he CF F91 f o r ce f ie ld . Th e d i f f e ren t pa r t

o f t he m ode l have been t e s t ed on m onom er p r ope r ti e s , th r ough com par i sons w i t h expe r i-

menta l resu l t s and ab in i t io ca lcula t ions , and on l iquid phase proper t i es us ing Molecular

D yn am i cs s i m u l a ti ons . Com par i sons w i t h p r ed i c ti ons f rom Mol ecu l a r D ynam i cs s im u l a -

t ions a re sa t i s fac tory .

6 A c k n o w l e d g e m e n t s

Th e f i nanc i al suppor t o f t he D R ET ( Pa r is ) ( Con t r ac t n ° 93 - 25 65A ) is g r ea t ly acknow l-

edged . We t ha nk a lso t he CN U SC ( Mont pe l li e r) fo r t he a l l oca t i on o f com pu t e r t i m e on an

I BM SP2 pa r a l l e l com pu t e r . O n o f u s ( I .B) w as supp or t ed by H ung a r i an O T K A T019308

and F029738.

R e f e r e n c e s

[1] D. Au rbach, Y . Gofer , B. -Z. M. , and C. Aped, J . Elec t roan a l . Chem . 339 (1992) 451.

[2] J . C. Soetens, C. Mii lot , and B. Maigret , J . Phys. Chem. A 102 (1998) 1055.

[3] W. Watanabe and R. M. Fuoss, J . Am. Chem. Soc. 78 (1956) 527.

[4] M . -G. Flore nt ino and T. R. A r turo , J . Ch em. E nd. D ata 29 (1984) 204.

[5] Ha ndbo ok of Chem istry and Physics vo l. 77 h Ed i t i on , C RC Pr e s s, Boka R a t on ,

Florida, 1996.

[6] M. S. Newman and R. A. Martele , J . Am. Chem. Soc. 94 (1972) 2733.

[7] E. E. Walker , J . appl . Chem. 2 (1952) 470.

[8] Krogh-Moe, J . Acta Cryst . 9 (1956) 951.

[9] Y. Tamura, E. Spohr, K. Heinzinger , G. P~i ink~s, and I . Bak5, Ber . Bunsenges. Phys,

Chem. 96 (1992) 147.

[10] I . BakS, G. P~l ink£s, and K. Heinzinger , Z. Naturforsch. 49a (1994) 967.

[11] P. M . M atias , G. A. Jeffrey, L. M. W ing ert , a nd J . R . Rub le, J . M ol . Stru( t .

(Theochem) 184 (1989) 247.


16/16

216

[12] C. J. Brown, A cta Crys t . 7 1954) 92.

[13] J. L. Aionso, A. D. Esposti , D. G. Lister, and P. Palmieri , J. Chem. Soc. , Faraday

Tran s 2 82 1986) 337.

[14] F. G. M ijlhoff, J. Mol. St ruc t. Theochem ) 36 1977) 334.

[15] S. J. Weiner, P. A. Kollman, D. T. Nguyen, and D. A. Case, J. Comp. Chem. 7

1986) 230.

[16] P. D aub er-O sgu thor pe, V. A. Ro berts, J. Wolff, M. Gen est , and A . T. H agler, Pro-

teins: Struc t . Func t. Ge net. 4 1988) 31.

[17] J . R. M aple, T . S. Th atch er, U. Diner, and A. T. Hagler, Chem ical Design Au tom a-

tion News 5 9 1990) 10.

[18] H. Sun, S. J. M umby, J. R. M aple, and A. T. Hagler, J. Am . Chem . Soc . 116 1994)

2978.

[19] J. E. Kilp atrick, K. S. Pitze r, and R . Spitzer, J. C hem . Soc . 1947 ) 2483.

[20] D. Crem er an d J. A . Pople, J. A m. Chem . Soc. 97 1975) 1358.

[21] H. A. Carlson, T. B. Nguyen, M. Orozco, and W. L. Jorgensen, J. Comp. Chem. 14

1993) 1240.

[22] C. Chipot and J. G. ~,ngy~n, GrtlO Version 3.0: Point Multipoles Derived From

Molecular Electrostatic Properties

QC PE n ° 66 5, 1994.

[23] H. C. Andersen , J. Co m pu t. Phys. 52 1983) 24.

[24] J. A. Bark er and R. O. Wa tts, M oi. Ph ys. 26 1973) 789.

[25] M. N eum ann , J. Che m. Phys . 82 1985) 5663.

[26] M. Ne um ann , J. Che m. Phys . 85 1986) 1567.

[27] M. P. Allen and D. J. Tildesley, Computer Simulations of Liquids Oxford Science

Publications, 1987.

[28] R. S. Bro dke y and H . C. Hershey, Transport Phenomena McGraw-Hil l In te rn a t iona l

Edit ion, 1988.

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