Electronic and phonon structure of nickel hydroxide: first-principles calculation study

We carried out a complete study (magnetic, electronic, lattice dynamic, and point defects) of the β-nickel hydroxide (β-Ni(OH)2) from first-principles calculations based on density functional theory. It is found that both of the magnetic ground state and band structure of β-Ni(OH)2 are strongly dependent on the correlation effect of Ni d-electrons. Experimental founded antiferromagnetic ground state with spin coupling along c direction has been confirmed by DFT+U method, and the predicated band structure shows a direct band gap about 3.5 eV with the highest occupied valence and lowest occupied bands mainly composed by O p-electron and Ni d-electron. Negative longitude acoustic phonon frequency around K point has been found, which is originated from the weak OH bond. High frequency localized vibration of hydrogen atom makes it easy to break away, and so form a vacancy, in agreement with the prediction that H+ vacancy has the lowest formation energy