Which of the following is not a Bravais lattice ?

Options

A. Face centred orthorhombic
B. Face centred cubic
C. Face centred tetragonal
D. End centred monoclinic

Answer

To determine which of the given options is not a Bravais lattice, we can analyze each option based on the characteristics of Bravais lattices.

### Step-by-Step Solution:

1. **Understanding Bravais Lattices**:
- Bravais lattices are distinct arrangements of points in space that represent the periodic structure of a crystal. There are 14 unique Bravais lattices in three-dimensional space.

2. **Analyzing the Options**:
- **Option A: Face Centered Orthorhombic**:
- This lattice has all angles equal to 90 degrees and unequal edge lengths. It is a valid Bravais lattice.
- **Option B: Face Centered Cubic (FCC)**:
- In this lattice, all edges are equal, and all angles are 90 degrees. It is also a valid Bravais lattice.
- **Option C: Face Centered Trigonal**:
- This lattice does not exist as a Bravais lattice. The trigonal system does not have a face-centered arrangement.
- **Option D: End Centered Monoclinic**:
- This lattice has unequal sides, with two angles at 90 degrees and one angle not equal to 90 degrees. It is a valid Bravais lattice.

3. **Conclusion**:
- Based on the analysis, the only option that is not a valid Bravais lattice is **Option C: Face Centered Trigonal**.

### Final Answer:
The option that is not a Bravais lattice is **C: Face Centered Trigonal**.