Simultaneous fitting of X-ray and neutron diffuse scattering data

Conventional crystallographic refinement uses the Bragg-peak intensities and gives the single-site average crystal structure. Information about short-range order and local order is contained in the diffuse scattering that is distributed throughout reciprocal space. Models of the short-range order in materials can now be automatically refined. The complementarity of X-ray and neutron diffraction data, and the value of simultaneously refining a structural model against both types of data, has long been known. This paper presents the first refinement of a short-range-order model against comprehensive X-ray and neutron diffuse scattering data simultaneously. The sample is the organic molecular crystal benzil, C₁₄H₁₀O₂ (for neutron work H is replaced by D). The technique gives new insights into local order in crystalline materials, including the dynamic correlation structure indicative of the dynamics of molecules in the crystalline state, and successfully overcomes limitations of using only the X-ray data set.

Computing details

Figures

(global)

Crystal data

C14H10O2	V = ? Å^3
Mr = ?	Z = 3
Hexagonal, P3121	? radiation, λ = ? Å
a = 8.402 (4) Å	× × mm
c = 13.655 (9) Å

Data collection

h = ?→?	l = ?→?
k = ?→?

Refinement

Fractional atomic coordinates and isotropic or equivalent isotropic displacement parameters (Ų)

	x	y	z	Uiso*/Ueq
C1	0.22769	0.1891	0.05171	0.06046
O2	0.26006	0.30833	0.11049	0.08678
C3	0.23178	0.02399	0.07512	0.05653
C4	0.28581	4e-05	0.16828	0.07205
C5	0.28707	−0.15598	0.1919	0.08544
C6	0.23469	−0.29195	0.12355	0.09545
C7	0.1776	−0.27425	0.03159	0.09010
C8	0.17871	−0.11356	0.00688	0.06432
H13	0.13691	−0.09678	−0.06495	0.06992
H11	0.13635	−0.38147	−0.02141	0.12424
H10	0.2345	−0.41559	0.1436	0.12697
H9	0.33114	−0.17244	0.26317	0.10761
H12	0.32663	0.10698	0.22142	0.09184

Atomic displacement parameters (Ų)

	U^11	U^22	U^33	U^12	U^13	U^23
C1	0.04488	0.04504	0.09145	0.02217	0.00017	−9.567e-05
O2	0.07383	0.07407	0.11243	0.03643	0.00039	−0.00017
C3	0.04267	0.04277	0.08417	0.02117	8.83325e-06	−8.683e-05
C4	0.06110	0.06125	0.09382	0.03031	−1.500e-06	−4.61e-05
C5	0.07509	0.07515	0.10610	0.03725	−0.000107	−8.196e-05
C6	0.08404	0.08358	0.11874	0.04135	−0.000125	−0.00025
C7	0.08229	0.08156	0.10644	0.04043	−8.01e-05	−0.00033
C8	0.05465	0.05436	0.08391	0.0269	−5.584e-05	−0.0002
H13	0.0657	0.06537	0.07871	0.0324	−2.148e-05	−0.000248
H11	0.1240	0.12279	0.1259	0.06086	−9.13e-06	−0.00055
H10	0.11605	0.1152	0.14958	0.05700	−0.000112	−0.000386
H9	0.1019	0.1022	0.11862	0.050768	−0.0001	−3.7e-05
H12	0.0861	0.08639	0.1030	0.04290	0.000132	−3.98e-05