PDF Editorial Staff Subcommittee Agenda and Minutes

PDF Editorial Staff Subcommittee
Wednesday, 19 March 2003
Conference Room D
ICDD Headquarters
Chairman - W.F. McClune

The meeting was convened by Frank McClune at 16:00.

1) The minutes of the March 2002 meeting were approved.

2) Quality Rating for Calculated Patterns

No rating exists at present.

Possible factors to consider:

σ cell parameters
σ bond distances and angles
σ coordinates
Magnitudes of temperature factors
Types of temperature factors (e.g., how extensive?)
Are the H atoms located?
Is the reduced cell used?
Calculated from single-crystal or powder data?
Year of publication (e.g., some older papers used a space group which has now been discredited)
What is the number of observed variables?
What is the range of atomic numbers in the composition (light vs. heavy elements)?
What is the volume of the unit cell?
Has the calculation been reviewed?
Has a prototype been assigned?
Type of experiment (X-ray diffraction, neutron diffraction, or electron diffraction)

A task group was appointed to determine if a quality mark for calculated patterns should be considered and what should be included in it. The members are:

S. Kabekkodu, chairman
J. Kaduk
C. Hubbard
P. Wallace
F. Rotella
E. Antipov
M. Bennett

3) Integrated Intensities

The use of peak heights vs. integrated intensities was discussed. Integrated intensities generally are preferred, partly because at high angles peaks tend to be broader and shorter compared to those at low angles. There are, however, other factors to consider. e.g., shoulders must be treated. POWD-12++ in its present configuration does not report the position of a shoulder properly. The position is given as that of the highest peak within the envelope.

It was suggested that the user should have the option of displaying the intensities either as peak heights or as integrated intensities. This was formalized as a motion to the Technical Committee.

MOTION: The PDF Editorial Staff Subcommittee recommends to the Technical Subcommittee that PDF-4 products include the option of displaying peak intensities as either peak heights or as integrated intensities.

The vote on this motion was 10 Yes, 0 No, 2 Abstain.

4) Extraction of Data from Papers

Editors are encouraged to include as much information as possible extracted from a paper. Examples are melting point, additional references, etc. These are included in the comments section.

5) Report on ICSD Duplicate Review

Frank McClune reported that the review has been completed. Not all changes have been keyboarded.

6) Calculated Pattern Review

Suri Kabekkodu gave a summary of his findings from this review. A copy of his overhead transparencies follows.

Incorrect Crystal Structures

Crystal lattice
i. Ignoring the possible higher symmetry
ii. Missing the super lattice
iii. Incorrect data abstraction (including missing decimal points)
iv. Wrong Bravais lattice
v. Wrong Z (no. of molecules per unit cell)

Space group
i. Unspecified use of non standard origin (e.g. P4/nmn at 2/m instead of -4m2)
ii. Incomplete information on author defined origins
iii. Improper transformations
iv. Structure refined in a wrong space group
v. Wrong site symmetry

i. Composition described by the structure differ significantly from the reported chemical formula
ii. Incorrect or unspecified atom in the structure/formula

Temperature Factors
i. Non positive definite anisotropic temperature factors
ii. Negative isotropic temperature factors
iii. Temperature factors that look unusual
iv. Incorrect abstraction of the type of temperature factors
v. Temperature factors of mixed type (e.g. Beta and Uiso)

i. Disordered structure without site occupancy refinement
ii. Disordered structure with poor site occupancy refinement

i. Physically impossible bond lengths and bond angles
ii. Wrong coordination polyhedron

7) Status of In-House Relational Database (RDB)

At present, the flat file and the RDB are being kept in synchronization. At some point in the future, the flat file will be archived.

Precision is being investigated. Many individual stored values have trailing zeroes which are not significant.

The meeting was adjourned at 17:48.

Respectfully submitted,
Harlan E. Clark