The unit cell with crystallographic dimensions, `a ne b ne c, alpha =gamma=90^(@) and beta ne 90^(@)` is :

Options

A. monoclinic
B. tetragonal
C. triclinic
D. orthorhombic

Answer

To solve the question regarding the type of unit cell based on the given crystallographic dimensions, we will analyze the characteristics of different crystal systems.

### Step-by-Step Solution:

1. **Understand the Given Conditions**:
- The unit cell has dimensions: \( a \neq b \neq c \)
- Angles: \( \alpha = \gamma = 90^\circ \) and \( \beta \neq 90^\circ \)

2. **Identify the Crystal Systems**:
- **Monoclinic**: In a monoclinic system, the conditions are:
- \( a \neq b \neq c \)
- \( \alpha = \gamma = 90^\circ \) and \( \beta \neq 90^\circ \)
- **Tetragonal**: In a tetragonal system:
- \( a = b \neq c \)
- \( \alpha = \beta = \gamma = 90^\circ \)
- **Triclinic**: In a triclinic system:
- \( a \neq b \neq c \)
- \( \alpha \neq \beta \neq \gamma \) (none are equal to 90°)
- **Orthorhombic**: In an orthorhombic system:
- \( a \neq b \neq c \)
- \( \alpha = \beta = \gamma = 90^\circ \)

3. **Match the Given Conditions with Crystal Systems**:
- The conditions \( a \neq b \neq c \) and \( \alpha = \gamma = 90^\circ \) while \( \beta \neq 90^\circ \) match the characteristics of the **monoclinic** crystal system.

4. **Conclusion**:
- Based on the analysis, the correct answer is that the unit cell described is **monoclinic**.

### Final Answer:
The unit cell with crystallographic dimensions \( a \neq b \neq c \), \( \alpha = \gamma = 90^\circ \), and \( \beta \neq 90^\circ \) is **monoclinic**.

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