Université de Fribourg

Anti-polarity in ideal BiMnO₃

Baettig, Pio ; Seshadri, Ram ; Spaldin, Nicola A.

In: Journal of the American Chemical Society, 2007, vol. 129, no. 32, p. 9854 -9855

The structure and properties of the possible multiferroic, BiMnO₃, are calculated using the LDA+U method of density functional theory. The symmetry is found to be centrosymmetric C2/c with zero ferroelectric polarization. The stereochemically active Bi lone pairs form local dipole moments which order in an anti-polar arrangement.

Université de Fribourg

Dissociative electron attachment and electron energy-loss spectra of phenyl azide

Živanov, Svetlana ; Ibanescu, Bogdan C. ; Paech, M. ; Poffet, Martine ; Baettig, Pio ; Sergenton, A.-C. ; Grimme, S. ; Allan, Michael

In: Journal of Physics B: Atomic, Molecular and Optical Physics, 2007, vol. 40, no. 1, p. 101-109

Electron-induced chemistry—dissociative electron attachment (DEA)—was studied for phenyl azide. The major fragment corresponded to the loss of N₂ and formation of the phenylnitrene anion. This process has an onset already at zero kinetic energy of the incident electron and is interpreted as proceeding via the A″π* electronic ground state of the phenyl azide anion. Other fragments,...

Université de Fribourg

First principles study of the multiferroics BiFeO₃, Bi₂FeCrO₆, and BiCrO₃: Structure, polarization, and magnetic ordering temperature

Baettig, Pio ; Ederer, Claude ; Spaldin, Nicola A.

In: Physical Review B, 2005, vol. 72(21), p. 214105

We present results of an ab initio density-functional theory study of three bismuth-based multiferroics, BiFeO₃, Bi₂FeCrO₆, and BiCrO₃. We disuss differences in the crystal and electronic structure of the three systems and show that the application of the LDA+U method is essential to obtain realistic structural parameters for Bi₂FeCrO₆. We calculate the magnetic...

Université de Fribourg

Ab initio prediction of a multiferroic with large polarization and magnetization

Baettig, Pio ; Spaldin, Nicola A.

In: Applied Physics Letters, 2005, vol. 86, p. 012505

We describe the design of a magnetic ferroelectric with large spontaneous magnetization and polarization using first-principles density functional theory. The usual difficulties associated with the production of robustly insulating ferromagnets are circumvented by incorporating the magnetism through ferrimagnetic behavior. We show that the ordered perovskite Bi₂FeCrO₆ will have a...

Université de Fribourg

Calculation of spin-orbit coupling within the LFDFT: Applications to [NiX₄]²⁻ (X=F⁻, Cl⁻, Br⁻, I⁻)

Atanasov, Mihail ; Rauzy, Cédrick ; Baettig, Pio ; Daul, Claude A.

In: International Journal of Quantum Chemistry, 2005, vol. 102, p. 119-131

Spin-orbit coupling has been introduced into our newly developed ligand field density functional theory (LFDFT), using the zero-order regular approximation as implemented into the Amsterdam density functional (ADF) code. Application of the formalism to a series of NiX₄²⁻ (X=F⁻, Cl⁻, Br⁻, I⁻) compounds shows the increasing importance of intra-ligand spin-orbit coupling across the F,...

Université de Fribourg

The calculation of ESR parameters by density functional theory: the g- and A-tensors of Co(acacen)

Atanasov, Mihail ; Baerends, Evert Jan ; Baettig, Pio ; Bruyndonckx, Raf ; Daul, Claude A. ; Rauzy, Cédrick ; Zbiri, Mohamed

In: Chemical Physics Letters, 2004, vol. 399(4-6), p. 433-439

The new DFT based ligand field (LF) model is proposed to calculate the g- and A-tensors of [Co(acacen)] that is known to be a difficult case. The results obtained are compared with the ZORA approach implemented in ADF as well as with the experimental values. The calculations are in good agreement with the experimental data and demonstrate the ability of the method to reproduce the large...