A controlled, one-step ammonolysis method with three different Fe/Ga ratios (70:30, 50:50, and 30:70) was used to synthesize functional nanocomposite materials consisting of 30−40 nm particles of γ′-Fe4N Fe4−x Ga x N phases in a GaN and Fe-doped GaN phase matrix. The γ′-Fe4N, Fe4−x Ga x N, and GaN phases were confirmed by the Rietveld analysis of the X-ray diffraction patterns, and the Fe-doped GaN phase was confirmed from Mössbauer spectroscopy and magnetization measurements. The magnetization of the superparamagnetic nanoparticles was expectedly reduced with the Ga incorporation in the samples. The coexistence of antiferromagnetic Fe4−x Ga x N and the ferromagnetic γ′-Fe4N phases resulted in an exchange bias effect (hysteresis loop shift of 28 Oe at 5 K) and a gradual magnetic phase transition from 250 to 55 K. Mössbauer spectroscopic analysis showed a hyperfine magnetic field distribution that the ab initio calculations duly supported. Ab initio calculations of the equilibrium lattice and Mössbauer hyperfine parameters were also performed.

Thermal programmed desorption spectra for chiral propylene oxide molecules adsorbed on Pd(111) are analyzed through dynamic Monte Carlo simulation and density functional theory calculations of the binding energy of adsorbed species. A model of the adsorbed phase is developed in such a way that the observed spectra are satisfactorily reproduced. The model reveals that propylene oxide adsorbs in configurations with different tilt angles, depending on the crowding of the surface around each adsorbed molecule, providing desorption energies varying over a wide range from about 9.2 to 13.6 kcal/mol.