How Do You Calculate Miller Indices for Complex Crystal Planes?

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In summary: I hope this helps you understand how the x-coordinate of 1/2 was determined. Keep in mind that this is just one possible solution and there may be other ways to approach this problem. In summary, we can use the given position coordinates and lattice vectors to determine the Miller indices of the cubic crystal plane and the intercepts with all coordinate axes can be found by finding the common factors of the intercepts.
  • #1
Akitirija
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Homework Statement



Determine the Miller indices of the cubic crystal plane that intersects the position coordinates
C (1, 1/4, 0), A (1, 1, 1/2), B (3/4, 1, 1/4), and all coordinate axes.


The Attempt at a Solution



This is an example problem with solution from Foundations of Materials Science and Engineering by Smith and Hashemi, so I already have the solution and I know the way to solve it. My only problem is the "and all coordinate axes" part of the problem.

The authors create a point D, which of course has the y-coordinate 1 and z-coordinate 0. However, I have no idea how to find the x-coordinate, which they just write is 1/2, without any explanation. I tried thinking about this in a trigonometric way, but I cannot see that I have enough to solve it trigonometrically either.

If anyone can explain to me how they conjured up the x-coordinate I would be very grateful!
 
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  • #2


Hello,

It seems like you are trying to determine the Miller indices of a cubic crystal plane using given position coordinates. This is a common problem in materials science and can be solved using a few steps.

First, we need to determine the three lattice vectors of the cubic crystal system. These are usually represented as a1, a2, and a3. In this case, we can assume that the a1 vector is parallel to the x-axis, a2 is parallel to the y-axis, and a3 is parallel to the z-axis.

Next, we need to find the intercepts of the plane with the three axes. For the x-axis, we can see that the plane intersects at the point C, which has coordinates (1, 1/4, 0). This means that the plane intercepts the x-axis at a distance of 1 unit from the origin. Similarly, for the y-axis, we can see that the plane passes through the point A, which has coordinates (1, 1, 1/2). This means that the plane intercepts the y-axis at a distance of 1 unit from the origin.

Now, for the z-axis, we can see that the plane passes through the point B, which has coordinates (3/4, 1, 1/4). This means that the plane intercepts the z-axis at a distance of 1/4 unit from the origin.

Using these intercepts, we can now determine the Miller indices of the plane. The Miller indices are given by (hkl), where h, k, and l are the reciprocals of the intercepts on the x, y, and z axes respectively. In this case, we have (1, 4, 4) as the Miller indices (since the intercepts are 1, 1, and 1/4).

Now, coming to the "and all coordinate axes" part of the problem, we need to find the intercepts of the plane with the coordinate axes. This means that we need to find the coordinates of a point on the plane that also lies on the x, y, and z axes. This can be done by finding the common factors of the intercepts we already have. In this case, the common factor is 1/4. So, we can create a point D with coordinates (1/4, 1/4, 0) which
 
  • #3
KataKoniK said:
Hello,

It seems like you are trying to determine the Miller indices of a cubic crystal plane using given position coordinates. This is a common problem in materials science and can be solved using a few steps.

First, we need to determine the three lattice vectors of the cubic crystal system. These are usually represented as a1, a2, and a3. In this case, we can assume that the a1 vector is parallel to the x-axis, a2 is parallel to the y-axis, and a3 is parallel to the z-axis.

Next, we need to find the intercepts of the plane with the three axes. For the x-axis, we can see that the plane intersects at the point C, which has coordinates (1, 1/4, 0). This means that the plane intercepts the x-axis at a distance of 1 unit from the origin. Similarly, for the y-axis, we can see that the plane passes through the point A, which has coordinates (1, 1, 1/2). This means that the plane intercepts the y-axis at a distance of 1 unit from the origin.

Now, for the z-axis, we can see that the plane passes through the point B, which has coordinates (3/4, 1, 1/4). This means that the plane intercepts the z-axis at a distance of 1/4 unit from the origin.

Using these intercepts, we can now determine the Miller indices of the plane. The Miller indices are given by (hkl), where h, k, and l are the reciprocals of the intercepts on the x, y, and z axes respectively. In this case, we have (1, 4, 4) as the Miller indices (since the intercepts are 1, 1, and 1/4).

Now, coming to the "and all coordinate axes" part of the problem, we need to find the intercepts of the plane with the coordinate axes. This means that we need to find the coordinates of a point on the plane that also lies on the x, y, and z axes. This can be done by finding the common factors of the intercepts we already have. In this case, the common factor is 1/4. So, we can create a point D with coordinates (1/4, 1/4, 0) which
hello, how did you get the last part of your solution? i do not get it.
 

1. What are Miller indices and why are they used?

Miller indices are a way to describe the orientation of a crystal plane in a lattice structure. They are used because they provide a simple and consistent way to identify and communicate the orientation of specific crystal planes.

2. How do you determine the Miller indices of a crystal plane?

To determine the Miller indices, you must first identify the intercepts of the plane on the three axes of the crystal lattice. Then, you take the reciprocal of each intercept, and simplify the resulting numbers to the smallest possible whole numbers. These numbers represent the Miller indices for that specific plane.

3. What is the significance of the numbers in Miller indices?

The numbers in Miller indices represent the relative spacing of atoms in a crystal plane. They can also provide information about the symmetry and orientation of the crystal lattice.

4. Can Miller indices be negative?

Yes, Miller indices can be negative. This usually occurs when the plane intercepts the negative axis of a crystal lattice.

5. How are Miller indices used in crystallography?

Miller indices are used to identify and classify different crystal planes, which can provide insight into the properties and behavior of a crystal lattice. They are also used to determine the orientation of a sample for experiments and analysis in crystallography.

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