Hello everyone,
I have synthesized NiMnSn alloy by ball milling technique. XRD study indicates that the system shows orthorhombic crystal structure. I have calculated lattice parameters manually by using equation. The calculated lattice parameters are a = 5.992, b = 6.245, c= 6,450.
Here we see that there is no much difference among the values of a,b, and c. Whereas in literature, I found significant difference among a,b,and c values.
Question1. Kindly let me know whether the calculated values are right and belongs to orthorhombic pattern or not?
Question 2: Is there any specific pattern to verify the a,b,c whether they belong to orthorhombic system or not.
Kindly answer this question.
"I have calculated lattice parameters manually by using equation", why manual ???
a = 5.992, b = 6.245, c= 6,450 >> this is significant.
Attached is the example of tetragonal system (a=b) with the lattice different of 0.01 A.
I have no idea how did you do it, but first this is no proof for a orthorhombic structure sind you only know the lattice parameters which already points out : LATTICE, no structure. Regarding the symmetry - and assuming your calculations are correct - your phase can be also monoclinic or triclinic. Taking into account pseudosymmetry it might be also possible that your symmetry is higher in case of overseen low-intensity peaks. ery unlikely, but as long as you do not show any experimental results it is hard to judges why do you assume this is the phase you are looking for. If it would be, the lattice parameters would have the expected size. And..as Maykel already pointed out: this is a significant difference! Please consider: only the structure decides about the symmetry, the lattice can have a higher which is not in contrast to the structure symmetry. Orthorhombic does not say a must be different to b and c but there are no conditions! This means, a=b=c is also permitted.
Please tell us, which are the expected lattice parameters, and post the diffractogram.
But in the literature which is the expected symmetry of this phase? Orthorhombic? Or maybe cubic? Certainly if the angles are 90 degrees and if your calculations are right is an orthorhombic system..you should give more information
@ I. Islah-u-din: You are incorrect! It is wrong to say " a, b, and c are not equal". It is correct to say: a, b and c can be different! This also includes, that they can be equal.
Try the following method. Start with the diffraction planes with two of the three lattice parameters are zero (e.g. 200 plane) and from which estimate a. From this value find the diffraction plane with l = 0, and estimate the value of b using the previous estimate a. Use a diffraction plane of non-zero hkl and estimate c. Repeat the procedure as many times as you can, then take an average.
To remove this problem, the lattice parameters can be calculated in accordance with the Nelson–Riley equation. For your information, you can find my paper"Quantitative analyses of TiC nanopowders via mechanical alloying method"
Try to use Maud Analysis or Rietica to feet the theoritical background with your results by Xrd.
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