Coverage for ase / constraints / fixed_plane.py: 100.00%

1from ase.constraints.constraint import ( 

2 IndexedConstraint, 

3 _normalize, 

4 _projection, 

5) 

6 

7 

8class FixedPlane(IndexedConstraint): 

9 """ 

10 Constraint object for fixing chosen atoms to only move in a plane. 

11 

12 The plane is defined by its normal vector *direction* 

13 """ 

14 

15 def __init__(self, indices, direction): 

16 """Constrain chosen atoms. 

17 

18 Parameters 

19 ---------- 

20 indices : int or list of int 

21 Index or indices for atoms that should be constrained 

22 direction : list of 3 int 

23 Direction of the normal vector 

24 

25 Examples 

26 -------- 

27 Fix all Copper atoms to only move in the yz-plane: 

28 

29 >>> from ase.build import bulk 

30 >>> from ase.constraints import FixedPlane 

31 

32 >>> atoms = bulk('Cu', 'fcc', a=3.6) 

33 >>> c = FixedPlane( 

34 ... indices=[atom.index for atom in atoms if atom.symbol == 'Cu'], 

35 ... direction=[1, 0, 0], 

36 ... ) 

37 >>> atoms.set_constraint(c) 

38 

39 or constrain a single atom with the index 0 to move in the xy-plane: 

40 

41 >>> c = FixedPlane(indices=0, direction=[0, 0, 1]) 

42 >>> atoms.set_constraint(c) 

43 """ 

44 super().__init__(indices=indices) 

45 self.dir = _normalize(direction) 

46 

47 def adjust_positions(self, atoms, newpositions): 

48 step = newpositions[self.index] - atoms.positions[self.index] 

49 newpositions[self.index] -= _projection(step, self.dir) 

50 

51 def adjust_forces(self, atoms, forces): 

52 forces[self.index] -= _projection(forces[self.index], self.dir) 

53 

54 def get_removed_dof(self, atoms): 

55 return len(self.index) 

56 

57 def todict(self): 

58 return { 

59 'name': 'FixedPlane', 

60 'kwargs': { 

61 'indices': self.index.tolist(), 

62 'direction': self.dir.tolist(), 

63 }, 

64 } 

65 

66 def __repr__(self): 

67 return f'FixedPlane(indices={self.index}, {self.dir.tolist()})'