What are the correct axial distance and axial angles for rhombohedral system?

Options

A. `a = b = c, alpha =beta = gamma != 90^@`
B. `a = b != c, alpha =beta = gamma = 90^@`
C. `a != b != c, alpha =beta = gamma = 90^@`
D. `a != b != c, alpha != beta != gamma != 90^@`

Answer

To determine the correct axial distance and axial angles for the rhombohedral system, we can follow these steps:

### Step 1: Understand the Rhombohedral System
The rhombohedral crystal system is one of the seven crystal systems in crystallography. In this system, the lengths of the axes are equal, but the angles between them are not 90 degrees.

### Step 2: Identify the Axial Distances
In the rhombohedral system, the axial distances are defined as:
- \( a = b = c \)

This means that all three axes (a, b, and c) have the same length.

### Step 3: Identify the Axial Angles
The angles in the rhombohedral system are defined as:
- \( \alpha \neq 90^\circ \)
- \( \beta \neq 90^\circ \)
- \( \gamma \neq 90^\circ \)

In the rhombohedral system, all three angles (alpha, beta, and gamma) are equal, but they are not equal to 90 degrees.

### Step 4: Conclusion
From the above information, we can summarize that for the rhombohedral system:
- Axial distances: \( a = b = c \)
- Axial angles: \( \alpha = \beta = \gamma \neq 90^\circ \)

Thus, the correct answer is that the axial distances are equal, and the axial angles are equal but not equal to 90 degrees.