The origin of the difference in structure between compounds containing CuCl 4 X 2 2−(X= H
2 O, NH 3) units is analyzed by means of first-principles calculations. While NH 3-containing
compounds display tetragonal symmetry, H 2 O-containing ones display an orthorhombic
distortion at low temperature where the equatorial Cl− ions are no longer equivalent. Our
simulations of optical and vibrational transitions show good agreement with all available
experimental optical absorption and Raman data. As a salient feature, the value of the force …

The origin of the difference in structure between compounds containing CuCl4X22?(X=
H2O, NH3) units is analyzed by means of first-principles calculations. While NH3-containing
compounds display tetragonal symmetry, H2O-containing ones display an orthorhombic
distortion at low temperature where the equatorial Cl? ions are no longer equivalent. Our
simulations of optical and vibrational transitions show good agreement with all available
experimental optical absorption and Raman data. As a salient feature, the value of the force …