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Neutron diffraction from nematic liquid crystal
Volume 48A, number 5
PHYSICS LETTERS
15 July 1974
NEUTRON DIFFRACTION FROM NEMATIC LIQUID CRYSTAL N. NIIMURA Laboratory of Nuclear Science, Tohoku University, Tomizawa, Sendai, 982, Japan Received 29 May 1974 The results of neutron scattering experiments of a fully deuterated para-azoxyanisole (PAA) extending over a wide momentum transfer range from 0.5 to 15 A’ are reported. The orientational correlations of the molecules are considered.
Scattering experiments performed at large momentum transfer Q(= 4ir sin0/X) contribute to the detailed understanding of the liquid crystalline state [1]. Neutron scattering experiments of a nematic para-azo~ xyanisole (PAA) have been made and the data can be explained on the basis of “single molecule” scattering [2]. But the observed range of momentum transfer was restricted to 3.6A’. In this letter we wish to report our recently observed preliminary results of neutron scattering experiments of a fully deuterated PAA extending over a wide momenturn transfer range from 0.5 to 15 A—’. We have used a time-of-flight neutron diffractometer the 300 MeV Tohoku University electron installed linac as aatpulse neutron source f 3]. The sample was sealed in a quartz tubing of thickness 0.3 mm and diameter 10mm, which could be heated electrically. Magnetic or electric fields are not applied to the sample.
tracting F1 (Q) from Sm(Q) and the result is shown in fig. 2. It can be seen that the peak at Q 1.8 A—’ is the contribution of the intermolecular correlation. In order to clarify the origin of the intermolecular correlation, the structure factor of the orientational correlations is calculated with the model that four kinds of orientations realized in the crystalline state of PAA [81 are dominant for the orientational correlations. The results are shown in fig. 2. The peak at 1.8 A—’ of could not be explained by the orientational correlations of the model. It is due to intermolecular distance main1 in Sm(Q) is mainly ly. The peaksbyatthe 3.2A’ and 5.7A—correlation, but as contributed intermolecular ace d
PAA Sm (Q)
The observed coherent structure factor Sm(Q) of d-PAA at 122°Chas been obtained after the corrections scatterings, and is shown in fig. 1. The peaks at Q 1.8 A’ and 3.2A~correspond to those at 20 30° of absorptions, multiple scatterings and incoherent and 54°observed by Pynn et al. [2] respectively. The structure factør Sm(Q) for molecular liquids is generally expressed as follows,
-
0.06
phase
~
5m(Q) = F 1(Q) + Sinter(Q) (1) where F1 (Q) is the form factor for a single molecule, and Sinter(Q) is the intermolecular scattering contribution and is entirely due to intermolecular distance and orientational correlations [4—6].By assuming the molecules as a rigid structure, F1(Q) can be calculated using molecular parameters of a crystalline state [7] as an approximation. Sinter(Q) has been obtained by sub-
002
C’
~0 .
~
(A
is
‘)
Fig. 1. Observed structure factor Sm(Q) for PAA.
375
Volume 48A, number 5
PHYSICS LETTERS
15 July 1974
and the experiment for the oriented sample are now in progress.
00”
sis d
14
0.03 0,02 ooi
Dr. M. Misawa for many helpful discussions.
~
The author wishes to thank Professor K. Suzuki and References
(1] -0.01 _O.02o
5
0
15
Q (A~) Fig. 2. Intermolecular scattering contributions Sinter(Q) and the calculated structure factor of the ‘orientational correlations.
seen clearly in fig. 2, the effect of the orientational correlations also exists in this part. The further analy-
376
P.G. de Gennes, Comp. Rend., 274B (1972) 142. [2] R. Pynn, K. Otnes and T. Riste, Solid State Commun., 11 (1972) 1365. [3] M. Misawa, Y. Fukushima, K. Suzuki and S. Takeuchi, Res. Reports Lab. Nuci. Sci. Tokohu Univ., 6 [1] (1973)
88.
14]
P.A. Egeistaff, D.I. Page and J.G. Powles, Molecular Phys., 20 (1971) 881. [51 J.G. Powles, Advances in Phys., 22 (1973) 1. [6] K.E. Gubbins, C.G. Gray, P.A. Egelstaff and M.S. Ananth, Molecular Phys., 25 (1973) 1353.
[71W.R. Kiigbaum, Y. Chatani and P.G. B26 (1970) 97.
Barber, Acta Cryst.,
PHYSICS LETTERS
15 July 1974
NEUTRON DIFFRACTION FROM NEMATIC LIQUID CRYSTAL N. NIIMURA Laboratory of Nuclear Science, Tohoku University, Tomizawa, Sendai, 982, Japan Received 29 May 1974 The results of neutron scattering experiments of a fully deuterated para-azoxyanisole (PAA) extending over a wide momentum transfer range from 0.5 to 15 A’ are reported. The orientational correlations of the molecules are considered.
Scattering experiments performed at large momentum transfer Q(= 4ir sin0/X) contribute to the detailed understanding of the liquid crystalline state [1]. Neutron scattering experiments of a nematic para-azo~ xyanisole (PAA) have been made and the data can be explained on the basis of “single molecule” scattering [2]. But the observed range of momentum transfer was restricted to 3.6A’. In this letter we wish to report our recently observed preliminary results of neutron scattering experiments of a fully deuterated PAA extending over a wide momenturn transfer range from 0.5 to 15 A—’. We have used a time-of-flight neutron diffractometer the 300 MeV Tohoku University electron installed linac as aatpulse neutron source f 3]. The sample was sealed in a quartz tubing of thickness 0.3 mm and diameter 10mm, which could be heated electrically. Magnetic or electric fields are not applied to the sample.
tracting F1 (Q) from Sm(Q) and the result is shown in fig. 2. It can be seen that the peak at Q 1.8 A—’ is the contribution of the intermolecular correlation. In order to clarify the origin of the intermolecular correlation, the structure factor of the orientational correlations is calculated with the model that four kinds of orientations realized in the crystalline state of PAA [81 are dominant for the orientational correlations. The results are shown in fig. 2. The peak at 1.8 A—’ of could not be explained by the orientational correlations of the model. It is due to intermolecular distance main1 in Sm(Q) is mainly ly. The peaksbyatthe 3.2A’ and 5.7A—correlation, but as contributed intermolecular ace d
PAA Sm (Q)
The observed coherent structure factor Sm(Q) of d-PAA at 122°Chas been obtained after the corrections scatterings, and is shown in fig. 1. The peaks at Q 1.8 A’ and 3.2A~correspond to those at 20 30° of absorptions, multiple scatterings and incoherent and 54°observed by Pynn et al. [2] respectively. The structure factør Sm(Q) for molecular liquids is generally expressed as follows,
-
0.06
phase
~
5m(Q) = F 1(Q) + Sinter(Q) (1) where F1 (Q) is the form factor for a single molecule, and Sinter(Q) is the intermolecular scattering contribution and is entirely due to intermolecular distance and orientational correlations [4—6].By assuming the molecules as a rigid structure, F1(Q) can be calculated using molecular parameters of a crystalline state [7] as an approximation. Sinter(Q) has been obtained by sub-
002
C’
~0 .
~
(A
is
‘)
Fig. 1. Observed structure factor Sm(Q) for PAA.
375
Volume 48A, number 5
PHYSICS LETTERS
15 July 1974
and the experiment for the oriented sample are now in progress.
00”
sis d
14
0.03 0,02 ooi
Dr. M. Misawa for many helpful discussions.
~
The author wishes to thank Professor K. Suzuki and References
(1] -0.01 _O.02o
5
0
15
Q (A~) Fig. 2. Intermolecular scattering contributions Sinter(Q) and the calculated structure factor of the ‘orientational correlations.
seen clearly in fig. 2, the effect of the orientational correlations also exists in this part. The further analy-
376
P.G. de Gennes, Comp. Rend., 274B (1972) 142. [2] R. Pynn, K. Otnes and T. Riste, Solid State Commun., 11 (1972) 1365. [3] M. Misawa, Y. Fukushima, K. Suzuki and S. Takeuchi, Res. Reports Lab. Nuci. Sci. Tokohu Univ., 6 [1] (1973)
88.
14]
P.A. Egeistaff, D.I. Page and J.G. Powles, Molecular Phys., 20 (1971) 881. [51 J.G. Powles, Advances in Phys., 22 (1973) 1. [6] K.E. Gubbins, C.G. Gray, P.A. Egelstaff and M.S. Ananth, Molecular Phys., 25 (1973) 1353.
[71W.R. Kiigbaum, Y. Chatani and P.G. B26 (1970) 97.
Barber, Acta Cryst.,