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Inorg@USF

木虫 (正式写手)

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在线: 133小时
虫号: 291411
注册: 2006-10-29
性别: GG
专业: 无机合成和制备化学

[交流] 【请教】三个A,B,C类警告，请指教！

Alert level A
PLAT223_ALERT_4_A Large Solvent/Anion  H    Ueq(max)/Ueq(min) ...    10.00 Ratio

（PLAT223 Type_4 Test Ueq(max)/Ueq(Min) range for H atoms in solvent
This test reports on large ranges in displacement parameters for hydrogen
atoms in the solvent/anion part of the structure.）
------------------------------------------
Alert level B
PLAT029_ALERT_3_B _diffrn_measured_fraction_theta_full Low .......    0.95

（ PLAT029 Type_3 Check _diffrn_measured_fraction_theta_full

Ideally (and a requirement for publication in Acta Crystallographica),
this fraction should be close to 1.0 for theta-full greater or equal
to sin(theta/lambda) = 0.6 (i.e. 25.24 degrees for MoKa and 67.7 degrees
for CuKa  radiation).
The three major causes of incomplete data sets are:
1 - A missing cusp of data due to data collection by rotation around
   the spindle axis only (standard on some image-plate systems).
   Cure: collect an additional data set after remounting the crystal.
2 - The DENZO imageprocessing package has problems with certain strong
   reflections. They are often excluded from the data set.
   Cure: Add an additional scan at lower power setting in order to
   include strong low order reflections.
3 - Incomplete scans, possibly based on erroneously assumed higher than
   actual symmetry.
Note: The default value of _diffrn_measured_fraction_theta_full that
is automatically calculated and inserted in the CIF by SHELXL-97 might
generate A-level ALERTS when significant numbers of reflections are
missing at higher theta values. In order to avoid such an ALERT,
substitute the values calculated with the SHELXL instruction 'ACTA 50'
for _diffrn_reflns_theta_full and _diffrn_measured_fraction_theta_full
respectively. For Mo-radiation, corresponding values of 25 degees (or
higher) and 0.99 (or higher) are expected.
PLATON may be used to analyse the case at hand (by invoking either the
'FCF-VALIDATION' mode or the 'ASYM-VIEW' mode).）
---------------------------------------------------------------------
Alert level C
PLAT245_ALERT_2_C U(iso) H10C Smaller than U(eq) C10    by ...    0.03 AngSq

（PLAT245 Type_2 Test for unusually low H-U(eq) as compared with bonded atom

U(iso) of a hydrogen atom is generally expected to be greater than the
U(eq) of the non-hydrogen atom it is attached to.)

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