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[求助]
有3个B错误,请大家帮忙解决一下已有1人参与
Alert level B
PLAT230_ALERT_2_B Hirshfeld Test Diff for O2 -- C1 .. 13.0 su
PLAT417_ALERT_2_B Short Inter D-H..H-D H2A .. H7A .. 1.87 Ang.
PLAT420_ALERT_2_B D-H Without Acceptor O7 - H8A ... ?
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分别为
PLAT230 Type_2 Hirshfeld Rigid-Bond Test (Acta Cryst (1976),A32,239-244
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The components of the anisotropic displacement parameters along chemical
bonds are assumed to be equal in magnitude. Large differences might
indicate contamination of these parameters with other (unresolved) effects
such as (substitutional) disorder, model or data errors and/or
over-refinement. Atomic sites assigned the wrong scattering type (e.g. Ag
versus Br) should generate 'problem signals' with this test. Data sets
corrected for absorption effects with DELREF techniques (e.g. DIFABS, SHELXA,
XABS2) often show large DELU values for bonds involving the heaviest atom.
Note: The original 'Hirshfeld-test' was defined in absolute terms (see
F.L.Hirshfeld, Acta Cryst. (1976). A32, 239-244). The current test is with
reference to the associated standard uncertainty.
PLAT417 Type_2 Test for short non-bonding inter D-H..H-D contacts
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Short non-bonding inter D-H..H-D contacts may be related to disordered or
misplaced H-atoms.
Experience has shown that any intermolecular H...H separation of less than
1.8 Angstroms between unit-occupancy H atoms is a clear indicator that one
or both of these H atoms may be wrongly placed.
PLAT420 Type_2 Test for D-H without acceptor
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Potential hydrogen bond donors are checked for the presence of suitable
acceptors using commonly used (Jeffrey) H-bond criteria. As a general rule
there should be an acceptor for each donor. Exceptions are very rare for O-H
and more common for -NH and -NH2. A common error is an -OH on a calculated
position pointing in the wrong direction.
[ Last edited by 魏超 on 2013-2-24 at 10:01 ] |
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