Implement TSC with CIF import/export and tests

qcrboxtools/cif/file_converter/cartesian.py

@@ -0,0 +1,45 @@
+import numpy as np
+
+
+def cell_constants_to_matrix(a: float, b: float, c: float, alpha: float, beta: float, gamma: float) -> np.ndarray:
+    """
+    Convert cell constants to a 3x3 cell matrix.
+
+    Parameters
+    ----------
+    a : float
+        Cell length a in Angstrom.
+    b : float
+        Cell length b in Angstrom.
+    c : float
+        Cell length c in Angstrom.
+    alpha : float
+        Cell angle alpha in degrees.
+    beta : float
+        Cell angle beta in degrees.
+    gamma : float
+        Cell angle gamma in degrees.
+
+    Returns
+    -------
+    np.ndarray
+        The 3x3 cell matrix.
+    """
+    alpha_rad = np.radians(alpha)
+    beta_rad = np.radians(beta)
+    gamma_rad = np.radians(gamma)
+
+    cos_alpha = np.cos(alpha_rad)
+    cos_beta = np.cos(beta_rad)
+    cos_gamma = np.cos(gamma_rad)
+    sin_gamma = np.sin(gamma_rad)
+
+    matrix = np.zeros((3, 3))
+    matrix[0, 0] = a
+    matrix[0, 1] = b * cos_gamma
+    matrix[0, 2] = c * cos_beta
+    matrix[1, 1] = b * sin_gamma
+    matrix[1, 2] = c * (cos_alpha - cos_beta * cos_gamma) / sin_gamma
+    matrix[2, 2] = c * np.sqrt(1 - cos_beta**2 - ((cos_alpha - cos_beta * cos_gamma) / sin_gamma) ** 2)
+
+    return matrix