An ordered low-temperature phase of barium nitroprusside trihydrate studied by neutron diffraction

Area of Science:

• Solid-state chemistry
• Crystallography
• Materials science

Background:

• Barium pentacyanonitrosylferrate trihydrate (barium nitroprusside trihydrate) is a coordination compound with potential applications.
• Understanding its structural behavior at low temperatures is crucial for material property prediction.

Purpose of the Study:

• To investigate the structural changes of barium nitroprusside trihydrate between 20 K and 120 K.
• To determine the crystal structure at 105 K using neutron diffraction.

Main Methods:

• Neutron diffraction was employed to study barium nitroprusside trihydrate crystals.
• Data was collected and analyzed across a temperature range of 20-120 K.

Main Results:

• A novel crystal phase was identified at 80 K, characterized by a duplicated 'a' lattice parameter, persisting down to 20 K.
• The crystal structure at 105 K exhibited ordered water molecules and P1 symmetry.
• Two of the four independent nitroprusside cations showed a rotation of 4.5 degrees around the [100] direction.

Conclusions:

• Barium nitroprusside trihydrate undergoes significant structural transitions at low temperatures.
• The observed phase transition and structural rearrangement at 105 K highlight the temperature-dependent nature of this compound's crystal lattice.