XRD.US is a full-service diffraction laboratory offering research grade powder and single crystal services for academy and industry. Our fast, accurate and customized services include data collection, qualitative and quantitative phase analysis, as well as in ab-initio structure determination with powder diffraction data, and Rietveld structure refinement, single crystal structure determination (Services).  We also provide consulting services on X-ray diffraction equipment, sampling, diffraction data collection strategies, powder diffraction data acquisition and data analysis software.

We offer several courses on advanced  powder diffraction methods, such as ab-initio structure determination with powder diffraction data, Rietveld refinement and  Rietveld phase quantification (Advanced Powder Diffraction Courses).

For your convenience we have easy navigation menu which will help you with placing of your Orders or choosing  diffraction equipment. You will find a lot of useful information about powder diffraction methods (TechNotes) and on how these methods are applied to solution of academic and industrial problems,  as well as links to websites where these topics are discussed in details (ApplNotes).

You will also be able to find brief description and links to X-ray diffraction hardware and software vendors, useful discussion forums etc.

Crystallite Size and Crystallite Size Distribution of Nanomaterials

Properties of materials are size dependent. It has been known that the electronic band structure of  for example semiconductor oxide is size dependent when its dimension is comparable with the exciton (Bohr) radius (the so-called Q-size effect).  It is also well known that it is practically impossible to prepare nanomaterials, crystals of which have exact same size. Crystallite size will have a certain, commonly, log normal distribution. Well known Scherrer equation will be practically useless to estimate the crystallite size distribution.  XRD.US offers crystallite size distribution determination services.

Please read our Technote 1014 and ApplNote 1016

Single Crystal Structure Determination

XRD.US has expanded its services into small molecule single crystal structure determination.

Full range of single crystal services, sample submission, order forms etc are described in Services section of our Catalogue.

Our prices are at least 50% less than those of our competitors.

Our capabilities include ambient, low temperature and high pressure studies.

You will not be turned down because of "bad crystals", twinned crystals", does not diffract well", "too busy" etc

Warren-Averbach crystallite size distribution

of cubic zirconia

Data acquisition

We will measure the diffraction pattern of  your samples as supplied, size- fractionated or otherwise instructed using following methods:

  • Laboratory X-ray diffractometer

  • Synchrotron radiation source

  • CW Neutron diffractometer

The raw data files will be collected with required scan parameters (step size, radiation source, wavelength etc), ASCII formatted  and mailed to you.  ...read more

Phase identification

We will identify the crystalline phases present in your sample using our X-ray powder diffraction data or your supplied data file. 

Question: What is the detection limit of powder diffraction method?

Our answer:  Normally 3-5 wt%, but with favorable scattering properties the minimal amount of could be lees than one weigh percent.

Question: Is Relative Intensity Ratio (RIR) method useful for determination of phases quantity?

Our answer: The RIR method is not applicable in most cases.  ...read more

Phase quantification

We will quantitatively determine weight (volume) percentage of crystalline and amorphous phases present in your sample.

Question: Absolute intensity of the strongest peak for Zincite is larger than that for Cristobalite (see left figure).  Does sample contain more Zincite than Crustobalite?

Our answer: No. There are 42.3% Cristobalite, only 16.5% Zincite in this sample.

...read more

Quantitative phase analysis by Rietveld method

(Theory and Hands-on course)

The course will consist of two components, the theory of Rietveld analysis and the practical application and use of software package for Rietveld analysis.

The course objective is to give a crystallographic and mathematical background of standardless Rietveld method and hands-on knowledge of modern Rietveld quantification software packages for academia, government and industry professionals.

This four day  course is offered twice annually (August and February) in the USA.

Question : What are the prerequisites for this course? 

Our answer: High school math and some basic knowledge of crystallography. ...read more

 

Ab initio structure determination

Suitable single crystals are not always available for structure determination. We can try to solve the structure using only powder data by ab-initio methods. Ab initio method is often required for  promising drug candidates.

Question : Is it possible to determine the structure of any compound by ab-initio methods?

Our answer: No, major obstacles are: large unit cell, too many independent atoms, or low symmetry, low sample crystallinity. Success of structure solution largely depends on quality and extracted structure factor amplitudes.

...read more

Consulting

We will advise you on diffractometer  purchase, data acquisition or treatment software, sampling and data collection strategies. Expert crystallographer will answer your questions that you could not resolve yourself.

Question : How many different Space Groups are shown below:  F12/d1; B112/b; B2/b11; C2/c11; I2/b11; C12/c1; F 2/d11

Our answer: Only one - C12/c1(#15).

Question : Is it a good idea to collect data using copper anode for iron-rich samples?

Our answer: No, use X-ray tube with cobalt anode.

Question : Does Scherrer equation give the crystallite size distribution?

Our answer: No. The crystallite size distribution is determined by Fourier methods, such as Warren-Averbach method.

...read more

 

 

 

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XRD.US    3590 Route 9, Suite 107, Cold Spring, New York 10516 USA. (Ph  845 208 7029. Fax 845 208 7030)