Molecular Sieve Zeolites-I

20 Refinement of the Crystal Structure

Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch020

of Laumontite VOLKER SCHRAMM and KARL F. FISCHER Lehrstuhl fuer Kristallographie, University of Saarbruecken, Germany A published crystal structure has been refined by least -squaresbased on about 8600 reflections measured with an automated three-circle single-crystal diffractometer. A dis tance least-squares computation (DLS) revealed the space group Am (No. 8) to be the most probable one. The pub lished structure was found to be essentially correct. The weighted R-factor for all reflections used is 9.4%. Further detailed work is in progress. A

p r i s m a t i c s p e c i m e n of l a u m o n t i t e f r o m the i s l a n d of M u l l , G r e a t B r i t a i n , w a s i n v e s t i g a t e d . Its size is 0.22 χ 0.09 X 0.08 m m , a n d its 3

lattice parameters are a

0

=

13.072 ± 0.012 A ; y =

c = 0

7.549 ±

0.008 A ; b

0

14.740 =b 0.015 A ;

=

111.9 ± 0 . 1 ° . T h e u n i t c e l l contains 4 f o r m u l a

units of C a [AI2S14O12] • ( ^ 4 H 0 ) . A n a u t o m a t e d Siemens s i n g l e - c r y s t a l 2

diffractometer was u s e d for m e a s u r i n g 8584 reflections w i t h N b - f i l t e r e d Mo-K

a

r a d i a t i o n . N o a b s o r p t i o n c o r r e c t i o n w a s necessary b e c a u s e of its

size. D u r i n g d a t a r e d u c t i o n , i n d i v i d u a l s t a n d a r d deviations w e r e assigned to the I F

o b s

I. T h e p u r p o s e of this s t u d y w a s to examine t h e details of the

l a u m o n t i t e structure first established b y B a r t l a n d F i s c h e r ( 2 ) . o n 1196 W e i s s e n b e r g film reflections, t h e y refined to

R ki h

=

Based

12.6%.

The

average s t a n d a r d d e v i a t i o n of t h e i r a t o m i c coordinates w a s r e p o r t e d as 0.03 A . Symmetry L a u e - g r o u p a n d e x t i n c t i o n rules suggest A2, Am,

a n d A 2 / m as the

p r o b a b l e space groups. B e c a u s e of the p y r o e l e c t i c b e h a v i o r of the crystals n o t e d b y C o o m b s ( 4 ) , o n l y a n a c e n t r i c space g r o u p is possible. I n o r d e r to d e d u c e the space g r o u p , a least-squares d i s t a n c e refinement u s i n g the m e t h o d of M e i e r a n d V i l l i g e r ( 9 ) w a s p e r f o r m e d for a l l 3 space groups. 259 In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

260

MOLECULAR SIEVE ZEOLITES


Table I.

Atomic Parameters y/bo

z/co

Β

0.7263(0) 0.2419(3) 0.3310(6) 0.7565(6) 0.1638(6) 0.8152(6) 0.2256(7) 0.6465(6)

0.2216(0) 0.7656(2) 0.2594(3) 0.3700(3) 0.4169(3) 0.5779(3) 0.6282(3) 0.7361(3)

0.5 0.5 0.3814(2) 0.3082(2) 0.3833(2) 0.3828(2) 0.3098(2) 0.3823(2)

1.69(4) 0.50(2) 0.75(3) 0.72(3) 0.77(3) 0.73(3) 0.62(3) 0.61(3)

0.273(1) 0.556(1) 0.933(1) 0.281(1) 0.752(1) 0.230(1) 0.752(1) 0.201(1) 0.752(1) 0.042(1) 0.705(1) 0.215(1) 0.419(1) 0.727(1) 0.249(2) 0.835(1)

0.2352(6) 0.2874(6) 0.3505(5) 0.3511(5) 0.3358(5) 0.4405(5) 0.4788(5) 0.5040(5) 0.5389(5) 0.6391(6) 0.6469(7) 0.6656(5) 0.7067(6) 0.7613(6) 0.3785(9) 0.6194(5)

0.5 0.3760(6) 0.3809(6) 0.3417(5) 0.1838(4) 0.5 0.3131(4) 0.3063(4) 0.5 0.3824(7) 0.3392(7) 0.1845(4) 0.3753(6) 0.5 0.1280(8) 0.1079(5)

1.10(10) 1.00(10) 0.92(8) 0.92(7) 1.13(7) 0.96(8) 1.30(7) 0.91(6) 0.82(8) 1.84(12) 1.81(12) 0.88(7) 1.50(9) 0.72(8) 5.64(23) 3.24(11)

Atom

x/a

Ca(l)Ca(2) Si(I) Al(II) Si(III) Si(IV) A1(V) Si(VI) 0(1) 0(2) 0(3) 0(4) 0(5) 0(6) 0(7) 0(8) 0(9) 0(10) 0(11) 0(12) 0(13) 0(14) 0(15) 0(16)

0

Site Ca(l)

0.90(5)

Ca(2)

Occupancies 0.88(4)

0.88(10)

0(15)

' The x- and y-coordinates of Ca(l) were held constant (see text).

Table II.

Interatomic Distances in Angstroms

Ca(l) -0(2) -0(3) -0(16)

2.479(9) 2.500(9) 2.421(8)

Ca(2) - 0 ( 1 0 ) -0(13) -0(15)

2.454(10) 2.465(9) 2.348(12)

-0(1) -0(2) -0(4) -0(12)

1.616(5) 1.595(9) 1.618(8) 1.587(7)

Al(II)-0(2) -0(3) -0(5) -0(7)

1.783(9) 1.742(8) 1.699(7) 1.617(7)

Si(III)-0(3) -0(4) -0(6) -0(8)

1.653(8) 1.630(8) 1.603(5) 1.573(7)

Si(IV)-0(7) -0(9) -0(10) -0(11)

1.635(7) 1.644(5) 1.607(9) 1.639(11)

A1(V) - 0 ( 8 ) -0(10) -0(12) -0(13)

1.770(7) 1.739(10) 1.741(7) 1.717(9)

Si(VI)-0(5) -0(11) -0(13) -0(14)

1.634(8) 1.634(10) 1.607(9) 1.646(5)

Sid)

In Molecular Sieve Zeolites-I; Flanigen, E., et al.; Advances in Chemistry; American Chemical Society: Washington, DC, 1974.

1

20.

Crystal Structures

S C H R A M M AND FISCHER

261

of Laumontite

Table III. Bond Angles in Degrees; Central A t o m is Vertex; Average Standard Deviations Ranging from 0.3 to 0.6 Degrees 106.0 111.2 108.1 109.2 113.1 109.2

0(7)-Si(IV) -0(9) -0(10) -0(11) -0(10) 0(9)-0(11) O(10)-o(ii)

105.0 113.2 108.4 108.1 113.0 109.3

0(2)-Al(II) -0(3) -0(5) -0(7) 0(3)-0(5) -0(7) 0(5)-0(7)

97.0 110.8 109.4 114.0 116.1 109.0

0(8)-Al(V)

-0(10) -0(12) -0(13) -0(12) -0(13) -0(13)

109.2 107.7 116.5 110.5 100.1 112.6

0(3)-Si(III)-0(4) -0(6) -0(8) 0(4) -0(6) -0(8) 0(6)-0(8)

109.2 108.9 107.2 104.6 107.6 119.1

0(5)-Si(VI) -0(11) -0(13) -0(14) -0(13) 0(H)-0(14) -0(14) 0(13)-

110.8 108.9 106.0 110.1 108.4 112.6

Si(I) -0(l)-Si(I) Si(I) -0(2)-Al(II) Al(II) -0(3)-Si(III) Si(I) -0(4)-Si(III) Al(II) -0(5)-Si(VI) Si(III)-0(6)-Si(III) Al(II) -0(7)-Si(IV)

147.5 138.5 128.0 137.0 136.2 144.2 143.3

Si(III)-0(8) -A1(V) Si(IV) -0(9) -Si(IV) Si (IV) - O ( 1 0 ) - A l ( V ) Si(IV) - 0 ( l l ) - S i ( V I ) Si(I) -0(12)-A1(V) A1(V) - 0 ( 1 3 ) - S i ( V I ) Si(VI) -0(14)-Si(VI)

138.2 137.5 131.9 137.0 135.2 139.9 138.4

0(l)-Si(I)

0(2)-


0(4)-

-0(2) -0(4) -0(12) -0(4) -0(12) -0(12)

0(10)0(12)-

T h e d i s t a n c e least-squares ( D L S ) c o m p u t a t i o n s (11)

were initiated on

t h e a t o m i c parameters of B a r t l a n d F i s c h e r ( 2 ) . T h e r e s u l t of this c o m p u t a t i o n favors t h e space g r o u p Am. A m i r o v et al. (1)

T h i s c o n t r a d i c t s the a s s u m p t i o n of

w h o a d o p t e d t h e space g r o u p A2.

F u r t h e r details of

D L S - c o m p u t a t i o n s w i l l b e p u b l i s h e d elsewhere. Refinement

of the

Structure

F o r refinement, w e a s s u m e d c o m p l e t e l y i o n i z e d atoms.

The full-

m a t r i x least-squares p r o g r a m L Q J L d e v e l o p e d f r o m S B L Q u t i l i z e s a n e x p o n e n t i a l p a r a m e t e r - r e p r e s e n t a t i o n of / - c u r v e s as f o l l o w s

(6)

7

F(s)

= exp { X η

a

n

· s ~ }, w i t h s = s i n θ/λ n

x

=1

T h e l a r g e set of d a t a a l l o w e d a p r o p e r c h o i c e of p a r t i a l d a t a sets f o r v a r i o u s groups of parameters to b e r e f i n e d , s t a r t i n g w i t h t h e p a r a m e t e r s given b y Bartl and Fischer (2).

F o r r e f i n i n g t h e scale f a c t o r a n d site



262


Figure 1.

Laumontite

A m , first setting, lower part of the unit cell, ordinates from 0.0 to 0.5

c-co-

o c c u p a n c i e s of C a a n d H 0 ( A - c y c l e s ) , a b o u t 130 d a t a w i t h s i n θ/λ 2

1

=

0.35 A " w e r e e m p l o y e d . F o r v a r y i n g coordinates a n d t e m p e r a t u r e factors 1

( B - c y c I e s ) , w e u s e d d a t a sets w i t h i n c r e a s i n g n u m b e r s of | F | starting o b s

w i t h the strongest ones a n d p r o c e e d i n g to a l l m e a s u r e d reflections.

Dur

i n g the progress of refinement, a sequence of one A - c y c l e a n d 2 B - c y c l e s w a s f o l l o w e d . W i t h i n t h e B - c y c l e s , the " h e a v y " atoms ( C a , S i , A l ) w e r e refined, k e e p i n g t h e other coordinates fixed. F o r v a r i a t i o n of coordinates a n d t e m p e r a t u r e factors of a l l atoms, the x- a n d [/-coordinates of C a 1 w e r e h e l d constant i n o r d e r to define the o r i g i n . S i m i l a r l y , o n l y the 2 C a o c c u p a n c i e s w e r e v a r i e d together w i t h the scale f a c t o r at t h e b e g i n n i n g of t h e A - c y c l e s . I n t h e subsequent A - c y c l e s , H 0 p o p u l a t i o n densities 2

w e r e a d d e d to the v a r i a b l e s . T h e final w e i g h t e d R - f a c t o r i n c l u d i n g a l l 8584 F

o b s

was 9.4%.

Description

of the

Structure

T a b l e s I , I I , a n d I I I present the refined a t o m i c coordinates as w e l l as the b o n d distances a n d angles. T h e setting u s e d (see

also F i g u r e 1)


20.

Crystal

S C H R A M M A N D FISCHER

Structures

of

263

Laumontite

is t h e same as g i v e n b y B a r t l a n d F i s c h e r ( 2 ) . T h e a l u m i n o s i l i c a t e f r a m e w o r k consists of b e n t 6-rings of ( S i / A l ) 0 - t e t r a h e d r a , w h i c h f o r m t h e 4

a s y m m e t r i c u n i t . T h e c o n c e n t r a t i o n of t h e A l - a t o m s i n t h e e q u i p o i n t s I I a n d V is p r o b a b l y i n c o m p l e t e as j u d g e d f r o m t h e A l - O - d i s t a n c e s . T w o " p u r e " S i O i 2 r i n g s — a l l p a r a l l e l to ( 1 1 0 ) — a r e 4

l i n k e d together

by 4

i s o l a t e d A l atoms f o r m i n g A l S i - c a g e s . E a c h cage is c o n n e c t e d w i t h its 4

8

n e i g h b o r b y 4 l i n k i n g o x y g e n atoms, r e s u l t i n g i n a c h a i n a l o n g t h e α-axis. F o u r o f these c h a i n s , w h i c h a r e l i n k e d together b y o n l y a f e w S i - O - A l bonds, surround a channel outlined b y substantially distorted

10-mem-

b e r e d r i n g s . T h e n a r r o w e s t cross-section of this c h a n n e l is 4.6 X 6.3 A ,


2

b a s e d o n 1.32 A i o n i c r a d i u s of o x y g e n . by 4 Ο and 2 H

2

T h e C a atoms a r e s u r r o u n d e d

0 i n nearly prismatic, six-fold coordination.

1,65. 31,64.

Ο "En Έ 1,62. ο λ

1,60. 137 13β

Figure

2.

Si-0-Si

angle

145

Κ7

β

Comparison of present data with that of Brown et al. (3)

B a s e d o n t h e S m i t h a n d B a i l e y d i a g r a m ( R e f . 10, F i g u r e 2 ) , a n d n e g l e c t i n g a l l o t h e r influences o n b o n d lengths, o n e w o u l d expect t h e f o l l o w i n g a p p r o x i m a t e A l contents of t h e t e t r a h e d r a l sites: 6 8 % i n A l ( I I ) , 15%

in Si(IV), 94% in A1(V), and 15% in Si(VI).

A s s u m i n g these

v a l u e s , o n e w o u l d o b t a i n a b o u t 1.9 A l atoms p e r 6 t e t r a h e d r a l sites, c o r r e s p o n d i n g to a b o u t 9 4 % average o c c u p a n c y of t h e 2 C a - e q u i p o i n t s . T h e C a o c c u p a n c i e s f o u n d i n this refinement c o r r e s p o n d t o this v a l u e w i t h i n their standard deviations. T h e T - O - T angles a r e s m a l l e r t h a n i n s i m i l a r structures ( 8 ) .

Three

of t h e 4 oxygens b o u n d t o C a atoms also h a v e T - O - T angles b e l o w a v e r age, i n agreement w i t h some other structures (e.g., R e f . 7). T a b l e I V represents a v e r a g e d T - O - T angles a n d T - O distances f o r d i f f e r e n t o x y g e n c o o r d i n a t i o n s a c c o r d i n g to T a b l e I I I o f B r o w n et al. (3).


264


Table IV.

Observed Mean T - O Bond Lengths and T - O - T

1

Angles


Coordination About Si

Al

Ca

Oxygens

2 1 1

0 1 1

0 0 1

6 4 4

T-O-T

Si-O 1.63 1.61 1.62

140.0 138.0 134.6

Al-O — 1.71 1.75

W e are i n g e n e r a l q u a l i t a t i v e agreement w i t h the results of these authors. In detail: (1)

T - O - T a n g l e decreases w i t h a n increase of t h e A l - a n d C a c o o r d i n a t i o n of o x y g e n .

(2)

T - O b o n d l e n g t h increases o w i n g to a n a d d i t i o n a l c o o r d i n a t i o n of C a to a n o x y g e n . ( 3 ) A p l o t of S i - O b o n d lengths vs. S i - O - S i b o n d angle s i m i l a r to B r o w n et al. (3) is s h o w n i n F i g u r e 2. T h e distances are d r a w n w i t h t h e i r respective s t a n d a r d deviations. T h e f u l l l i n e is the regression l i n e of t y p e b (see Ref. 3, T a b l e I I ) . O u r d a t a s u g gest a steeper slope ( b r o k e n l i n e ) . T h i s m u s t not b e significant because the A l content of the Τ atoms is n o t y e t w e l l k n o w n a n d because w e h a v e too f e w d a t a . J u d g i n g these observations, one has to k e e p i n m i n d t h a t t h e refinement of the structure is p r e s e n t l y at a n i n t e r m e d i a t e stage. results a p p e a r to s u p p o r t the ideas of B r o w n et al. (3) based on Cruickshank's theory

Our preliminary o n d-p π b o n d i n g

(5).

A n i s o t r o p i c refinement, i n v e s t i g a t i o n of the H 0 sites, a n d d e t e r m i n a 2

t i o n of the S i / A l d i s t r i b u t i o n is i n progress. Acknowledgment T h a n k s are d u e to the D e u t s c h e F o r s c h u n g s g e m e i n s c h a f t , w h o s u p p o r t e d the project.

W e also t h a n k the I n s t i t u t f u e r N e u t r o n e n p h y s i k I

( T . S p r i n g e r , d i r e c t o r ) of the K e r n f o r s c h u n g s a n l a g e , J u e l i c h , f o r p r o v i d ing computer time.

S o m e p r e l i m i n a r y c o m p u t a t i o n s w e r e d o n e at the

Deutsches Rechenzentrum, Darmstadt.

Literature Cited (1) Amirov, S. T., Ilyuchin, W. W., Belov, N. W., Dokl. Akad. Nauk SSSR 1967, 174, 667-670. (2) Bartl, H., Fischer, K. F., Neues Jahrb. Mineral. Monatsch. 1967, 2/3, 33-42. (3) Brown, G. E., Gibbs, G. V., Ribbe, P. H., Am. Mineralogist 1969, 54, 1044-1061. (4) Coombs, D. S., Am. Mineralogist 1952, 37, 812-830. (5) Cruickshank, D. W. J., J. Chem. Soc. 1961, 5486-5504.


20.

SCHRAMM

AND

FISCHER

Crystal

Structures

of

Laumontite

Fischer, K. F., Z. Krist. 1968, 127, 110-120. Fischer, K. F., Schramm, V., ADVAN. CHEM. SER. 1971, 101, 250. Liebau, F., Acta Cryst. 1961, 14, 1103-1109. Meier, W. M., Villiger, M., Z. Krist. 1969, 129, 411-423. Smith, J. V., Bailey, S. W., Acta Cryst. 1963, 16, 801-811. Villiger, H., "DLS—A FORTRAN Computer Program for the LeastSquares Refinement of Interatomic Distances," Institut fuer Kristallographie und Petrographie, Eidg. Technische Hochschule, Zuerich, 1969. RECEIVED February 13, 1970. Downloaded by UNIV OF CALIFORNIA SAN DIEGO on June 1, 2015 | http://pubs.acs.org Publication Date: August 1, 1974 | doi: 10.1021/ba-1971-0101.ch020

(6) (7) (8) (9) (10) (11)

265


Molecular Sieve Zeolites-I

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