Data Mining with DDView+
and the PDF-4 Databases
FeO Non-stoichiometric Oxides
Some slides of this tutorial have sequentially-layered
information that is best viewed in ‘Slide Show’ mode
This is one of three example-based tutorials for using the
data mining capabilities of DDView+ with the PDF-4+
database and it covers the following topic:
• FeO Non-stoichiometric Oxides
– sorting out temperature and stoichiometric effects
on cell parameters
Two other similar tutorials for data mining exist and
cover the following topics:
• CIGS Photovoltaics
– solid solution / cell parameter relationship
• Carbamazepine Polymorphs
– a PDF-4/Organics application
– investigating polymorphic forms of an active
pharmaceutical ingredient (API)
Stoichiometric Factors Affecting the
Diffraction Pattern of FeO
• FeO is frequently non-stoichiometric with
Fe-site vacancies.
• These defects have crystallographic effects
and can cause shifts in the observed powder
diffraction peaks.
• Summaries of this effect can be “mined”
from the PDF-4+ database and displayed for
further study.
Ideal Crystal Structure of FeO*
Cubic System
Space Group: Fm-3m
NaCl type structure
*Structure taken from PDF entry 04-004-7638 calculated from the LPF database.
Data Mining for FeO Entries: Step 1
Use the Preferences Window to establish what will be displayed in
the Search Results table . . .
1. Click the ‘Preferences’ icon
1. Click the ‘Preferences’ icon
2. Click the ‘Search’ tab in the
‘Preferences’ window
Selecting Fields for the Results Table
Selected Fields:
Use these buttons
to move a selected
item up or down in
the listed order for
the results table.
Available Fields:
Use these buttons to move selected items between the
‘Available Fields’ list of 60 items and the ‘Selected Fields’
list of items that will be displayed in the results table.
Selecting Fields for Results Table (FeO)
Setting up the fields as shown
here will serve the purposes of
this example.
Chemistry Criterion for Search: Fe and O only
entered on ‘Periodic Table’ tab of ‘Search’ window
Once entered, the chemistry
criterion can be verified here.
Then click ‘Only’ . . .
Finally click ‘Add’ to include
this criterion for the search.
First click elements Fe and O . . .
Structure Criterion for Search: FCC Space Group #225 – ‘Fm-3m’
entered on ‘Structures’ tab of ‘Search’ window
Perform search using
specified chemistry
and space group
criteria.
Results of DDView+ Search for FeO
A total of 63 entries for Fe1-xO compounds
Analysis of the Resulting Database Entries
Most fields in the results table can be graphically illustrated in
either X-Y plot or histogram form.
For the current application, we will use an X-Y plot to illustrate the
a-axis cell parameter as a function of atomic % Fe.
To do this, ‘Graph Fields…’ is first selected from the ‘Results’ drop
down menu of the ‘Results’ window.
Choose X-axis field
from drop down
menu: ‘Atomic %’
Choose element
for Atomic %
values from drop
down menu: ‘Fe’
Choose Y-axis field
from drop down
menu: ‘XtlCell-a’
Click ‘OK’ to
draw Graph
FeO a-axis Cell Parameter vs. Atomic % Fe
Stoichiometric – 1:1
High Temperature
Ambient
• This graph shows little apparent correlation between atomic % Fe and a-axis.
• Note that entries reported as being stoichiometric (1:1) are in a vertical line at
right (50 at% Fe). All others report less than stoichiometric amounts of Fe.
• Further examination of individual entries separates ambient and high
temperature determinations of the a-axis.
• Individual entries from this chart may be examined by left-clicking on individual
spots. The circled spot corresponds to the entry on the next slide.
PDF Card for FeO (01-073-2144)
Fe.942O
The ‘PDF’ tab of this window displays
the actual formula and stoichiometry.
PDF Card for FeO (01-073-2144)
This window may be closed to return to the
previous graphical plot of ‘a’ vs. atomic % Fe.
The ‘Experimental’ tab of this window shows (among other
things), the source of the information. Authors, in this case,
are B.T.M. Willis & H.P. Rooksby.
FeO a0 Cell Parameter vs. Atomic % Fe
Stoichiometric – 1:1
Stoichiometric – 1:1
High Temperature
High Temperature
Ambient
Ambient
Choosing another entry from the graph (circled in blue), one
can bring up the information shown on the next slide.
PDF Card for FeO (01-074-1880)
Fe.9536O
Reported stoichiometry for this
entry is shown on the ‘PDF’ tab.
PDF Card for FeO (01-074-1880)
Close window to return to
search results graph.
The reference shown on the
‘Experimental’ tab, for this entry,
cites a study by E.R. Jette & F.
Foote.
FeO a0 Cell Parameter vs. Atomic % Fe
Stoichiometric – 1:1
High Temperature
Ambient
1 2 3 4 5 6 7 8 9
A number of points on this graph
appear to be linearly aligned with
the two examined thus far.
One could check the references
of these points to determine if
they are from the same sources.
1.
2.
3.
4.
5.
6.
7.
8.
9.
Formula
Fe0.942O
Fe0.9536O
Fe0.9570O
Fe0.9630O
Fe0.9646O
Fe0.9712O
Fe0.9712O
Fe0.974O
FeO
Reference
Willis & Rooksby
Jette & Foote
Jette & Foote
Jette & Foote
Jette & Foote
Jette & Foote
Jette & Foote
Willis & Rooksby
Jette & Foote
Combining the FeO Data from Just the Willis &
Rooksby and Jette & Foote Sources
• To analyze the apparent relationship within the roughly linear data
identified in the previous slide, the data must be limited to just
the sources identified.
• A particular author can be added to the search criteria to restrict
results to just that author.
• Results of multiple searches can be combined, such as results
found from two different sources.
• This process is outlined here and illustrated on the next few slides:
– Add author ‘Willis’ criterion to previous FeO search and perform search
– Change author ‘Willis’ to author ‘Jette’ and perform search again
– Combine results from these two searches via the ‘History’ tool
Search FeO Structures for Author ‘Willis’
With the ‘Just (Fe And O)’ and ‘Space Group #225’ still in place on
their respective tabs on the ‘Search’ window, the author ‘Willis’ can
be added to the ‘References’ tab and the search performed.
2 Results
The results of this, and any other ‘Search’, are automatically saved in the
‘History’ file and can be accessed for the duration of the DDView session.
Search FeO Structures for Reference ‘Jette’
Similarly, a second search is performed substituting author ‘Jette’ for
‘Willis’ of the previous search.
7 Results
Use of the ‘History’ Tool to Combine Searches
The ‘History’ feature is accessed via the ‘Tools’ menu.
Combine the Results of These Two Searches
The top area shows a history of searches performed during
this session. These searches may be individually selected and
copied
to the searches
‘Combinedmay
Searches’
area via
the‘And’
down
The selected
be combined
with
to arrow
include
button.
Alternatively,
they
can both
be searches
selected using
only those
entries that
appear
in both
or with‘Ctrl-click’
‘Or’ to
and copied
together
viaappear
the down-arrow
button.For this
include
all entries
that
in either search.
exercise, we are interested in all entries, so ‘Or’ is chosen,
then the ‘Combined Results’ button performs the operation.
Combined Author Results for FeO Entries
The results table includes all 9 entries,
which may be graphed similarly to the
way the original 63 hits were graphed.
‘Atomic % Fe’ vs. ‘XtlCell-a’
Click ‘OK’ to create graph
Graph of FeO Cell Parameters derived by
Willis & Rooksby and Jette & Foote
These data may be exported to a ‘.csv’ file for more involved
mathematical or statistical analysis using a spreadsheet program. For
example, one could explore whether these data are linear (Vegard’s Law)
or if there is a systematic (and significant) deviation from linearity.
FeO a-axis Cell Parameter vs. Atomic % Fe
- High Temperature Studies
Stoichiometric – 1:1
High Temperature
Ambient
Several entries from this high temperature region reference
a single study, “Point Defect Clusters in Wuestite” by Radler,
Cohen, & Faber, J. Phys. Chem. Solids, 51, 217 (1990). To
quickly examine which points come from this study, the
search can be reperformed using one of these authors.
Change Author for Search
On the ‘References’ tab, ‘Radler’ (or
‘Cohen’ or ‘Faber’) can be entered in the
‘Author’ field to obtain the desired PDF
entries. The ‘Structures’ and ‘Periodic
Table’ tabs contain the previously
entered information regarding FeO and
space group 225. This search will yield
the 13 entries found on the next slide.
PDF Entries from Radler, Cohen, & Faber Study (1990)
The a-axis cell parameter for just these
entries can now be plotted vs. atomic % Fe
and the resulting graph is shown on the
following slide.
Graph of Radler, Cohen, and Faber FeO Entries
1
2
1. Data for varying T from 1123 to 1373 C with slightly increasing O content
2. Data for varying stoichiometry at 1323 C from Fe0.88O to Fe0.95O
Another Look at FeO results - Density
Return to the original list of 63 FeO entries . . .
Choose the original search:
{Only (Fe And O)} And {International
Space Group Number Exactly ‘225’}
and click the ‘Results’ button.
Use the ‘History’ icon to
retrieve any searches already
performed during this session
of DDView+.
Another Look at FeO results - Density
Another way to analyze this data is to
look at the density as a function of cell
parameter. This is performed by using the
‘Results’ drop down menu to access
‘Graph Fields…’
Results: density vs. a axis cell
parameter for reported FeO structures
Entries with 1:1 atomic ratio reported for FeO
Density is inversely proportional to cubic cell parameter
“An -ray Study of the Wuestite (FeO) Solid Solutions”
- Jette & Foote & “Change of Structure of Ferrous
Oxide at Low Temperature” - Willis & Rooksby.
Density increases very slightly as cell parameter goes
up with increasing Fe content.
“Point Defect Clusters in Wuestite” - Radler, Cohen, & Faber
Density decreases as a axis increases (inverse relationship) as T
is varied from 1123 to 1373 C with slightly increasing O content
Both density and a axis increase dramatically as stoichiometry
at 1323 C is increased from Fe0.88O to Fe0.95O.
Summary for Non-stoichiometric Cubic FeO
• Multiple explanations exist for unit cell parameter
variations in non-stoichiometric FeO in the PDF
• Systematic studies regarding stoichiometry and/or
temperature can be “mined” from the database
• No single relationship describes all the data, thus
different “defect” arrangements must exist for these
materials
• Ability to access PDF entries directly from graphs’
facilitates obtaining other data and references
Thank you for viewing our
tutorial. Additional tutorials are
available at the ICDD web site
(www.icdd.com).
International Centre for Diffraction Data
12 Campus Boulevard
Newtown Square, PA 19073
Phone: 610.325.9814
Fax: 610.325.9823