Date of Issue:
27 February 2024

Standard Reference Material 640g
Line Position and Line Shape Standard for Powder
Diffraction (Silicon Powder)

C ERTIFICATE
Purpose: The certified values delivered by this Standard Reference Material (SRM) are intended for the calibrationof powder diffraction equipment with respect to line position and profile breadth as a function of 2 angle.
Description: A unit of SRM 640g consists of approximately 7.5 g of silicon powder bottled under argon.
Certified Values: The certified value for the lattice parameter is shown in Table 1. Metrological traceability is tothe International System of Units (SI). Units for lattice parameter dimension is length (expressed as nanometers). The
certified values and uncertainties were calculated according to the method described in the ISO/JCGM Guide [1,2].
The certification procedure can be found in reference 3.
Table 1. Certified Lattice Parameter for SRM 640g
Lattice Parameter(nm)
aExpanded Uncertainty(k = 2)0.543 110 9

 0.000 008 0

Non-Certified Values: Non-certified values are provided in Appendix A.
Period of Validity: The certified value delivered by SRM 640g is valid indefinitely, within the measurement
uncertainty specified. The certified values are nullified if the material is stored or used improperly, damaged,contaminated, or otherwise modified. Periodic recertification of this SRM is not required.
Maintenance of Certified Values: NIST will monitor this SRM over the period of its validity. If substantive
technical changes occur that affect the certification, NIST will issue an amended certificate through the NIST SRM
website (https://www.nist.gov/srm) and notify registered users. SRM users can register online from a link available
on the NIST SRM website or fill out the user registration form that is supplied with the SRM. Registration will
facilitate notification. Before making use of any of the values delivered by this material, users should verify they havethe most recent version of this documentation, available through the NIST SRM website (https://www.nist.gov/srm).

R. David Holbrook, ChiefMaterials Measurement Science Division

SRM 640g

Steven J. Choquette, Director
Office of Reference Materials

Page 1 of 3

Storage: SRM 640g was bottled under argon to protect against humidity. When not in use, store the unused portionof this powder tightly capped in the original bottle or in a manner with similar or greater protection against humidity.
Use: The loading of samples for Bragg-Brentano diffractometers should be performed so as to achieve a powder bedof a high packing density and a flat surface.
REFERENCES
[1]

[2]

[3]

Beauchamp, C.R.; Camara, J.E.; Carney, J.; Choquette, S.J.; Cole, K.D.; DeRose, P.C.; Duewer, D.L.;
Epstein, M.S.; Kline, M.C.; Lippa, K.A.; Lucon, E.; Molloy, J.; Nelson, M.A.; Phinney, K.W.; Polakoski, M.;
Possolo, A.; Sander, L.C.; Schiel, J.E.; Sharpless, K.E.; Toman, B.; Winchester, M.R.; Windover, D.;
Metrological Tools for the Reference Materials and Reference Instruments of the NIST Material Measurement
Laboratory; NIST Special Publication (NIST SP) 260-136, 2021 edition; National Institute of Standards andTechnology,Gaithersburg, MD(2021);
availableat
https://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.260-136-2021.pdf (accessed Feb 2024).
JCGM 100:2008; Evaluation of Measurement Data — Guide to the Expression of Uncertainty in Measurement(GUM 1995 with Minor Corrections); Joint Committee for Guides in Metrology (2008); available athttps://www.bipm.org/en/committees/jc/jcgm/publications (accessed Feb 2024); see also Taylor, B.N.;
Kuyatt, C.E.; Guidelines for Evaluating and Expressing the Uncertainty of NIST Measurement Results; NISTTechnical Note 1297; U.S. Government Printing Office:Washington, DC (1994); available athttps://www.nist.gov/pml/nist-technical-note-1297 (accessed Feb 2024).
Cline, J.P.; Mendenhall, M.H.; Black, D.; Henins, A.; Prothero, J.B.; Certification of Standard Reference
Material 640g Line Position and Line Shape Standard for Powder Diffraction (Silicon Powder); NIST Special
Publication 260-245; National Institute of Standards and Technology, Gaithersburg, MD (2024); available athttps://nvlpubs.nist.gov/nistpubs/SpecialPublications/NIST.SP.260-245.pdf (accessed Feb 2024).

If you use this SRM in published work, please reference:
Cline JP, Mendenhall MH, Black D, Henins A, Prothero JB (2024) Certification of Standard Reference Material 640g
Line Position and Line Shape Standard for Powder Diffraction (Silicon Powder). (National Institute of Standards andTechnology, Gaithersburg, MD), NIST Special Publication (SP) 260-245. https://doi.org/10.6028/NIST.SP.260-245
Certain commercial equipment, instruments, or materials may be identified in this Certificate of Analysis toadequately specify the experimental procedure. Such identification does not imply recommendation or endorsementby the National Institute of Standards and Technology, nor does it imply that the materials or equipment identified
are necessarily the best available for the purpose.
Users of this SRM should ensure that the Certificate in their possession is current. This can be accomplished bycontacting the Office of Reference Materials 100 Bureau Drive, Stop 2300, Gaithersburg, Maryland 20899-2300;
telephone (301) 975-2200; e-mail srminfo@nist.gov; or the Internet at https://www.nist.gov/srm.

* * * * * * * * ** * * End of Certificate * * * * * * * * ** * *SRM 640g

Page 2 of 3

A PPENDIX A
Non-Certified Values: Non-certified values are suitable for use in method development, method harmonization, andprocess control but do not provide metrological traceability to the SI or other higher-order reference system. The
analyses associated with certification of SRM 640g included the computation of the diffraction line positions shownin Table A1.
Table A1. Non-Certified Peak Position Values for SRM 640g,
Computed Using Cu Kα Radiation, λ = 0.154 059 29 nm
hkl

2(degrees)

123434
54
56
512
1032
143
2
3

10
10
12
10
103

28.44147.30156.12069.12776.37388.02694.948106.703
114.086
127.537
136.883

Period of Validity: These non-certified values are valid indefinitely within the measurement uncertainty specified.
The value assignments are nullified if this material is stored or used improperly, damaged, contaminated, or otherwise
modified.
Maintenance of Non-Certified Value: NIST will monitor this material to the end of its period of validity. If
substantive technical changes occur that affect the non-certified values during this period, NIST will update thisAppendix and notify registered users. SRM users can register online from a link available on the NIST SRM website
or fill out the user registration form that is supplied with the SRM. Registration will facilitate notification. Before
making use of any of the values delivered by this material, users should verify they have the most recent version ofthis documentation, available through the NIST SRM website (https://www.nist.gov/srm).

* * * * * * * * * * * End of Appendix A * * * * * * * * * * *SRM 640g

Page 3 of 3