Rotational Brownian dynamics simulations of non-interacting magnetized ellipsoidal particles in d.c. and a.c. magnetic fields

Brownian dynamics simulation of a dispersion composed of disk-like hematite particles regarding the orientational distribution and the magneto-rheological properties

“…Ordinary magnetic particles are ferromagnetic, as in the case of magnetite, and they are usually magnetized in the particle axis direction, which gives rise to the significant orientational feature of a single-peak orientational distribution under the circumstance of an applied magnetic field and a flow field [25][26][27][28][29][30][31]. In contrast, hematite particles exhibit quite different characteristics because they are magnetized in a direction normal to the particle axis direction, and exhibit much weaker magnetization than magnetite [32][33][34][35].…”

Relaxation in x-space Magnetic Particle Imaging

“…The competition of these torques causes a phenomenon known as relaxation, which delays the magnetization response of SPIOs and is typically described by a first-order Debye relaxation process [14], [15]. Relaxation descriptions for particle magnetization have been studied in ferrofluid literature [15]- [21], primarily for Néel and Brownian relaxation time constants, which are based on thermal processes. Based on this literature, comprehensive models of non-adiabatic MPI magnetization have been derived [22].…”

Chameleon behaviour of a-synuclein : brownian dynamics simulations of protein aggregation

“…Hagan and Chandler [78] and Sánchez and Rinaldi [169] use quaternions q as orientation coordinates and propagate them according to ∆q = (∂q/∂φ b )∆φ b ; they do not discuss the correction terms. In a series of papers, Naess, Elgsaeter and co-workers [55,56,57,58,131] derived an equation of motion for the rotation vector a and validated the approach by numerical tests.…”

“…The few reported RBD studies are based on straightforward extensions of translational Brownian dynamics, while surprising little attention has been paid to validating the resulting algorithm [41,84,135,169]. The development of a proven RBD algorithm by Elgsaeter, Naess and co-workers inspired us to apply their technique to patchy particle simulations.…”

“…These require an additional Brownian equation of motion for the orientation of the symmetry axis of the rod, while the rotations around this axis are ignored. The rotations of anisotropic colloids, which represent the most generalised class of rigid particles, is more difficult to simulate by the Brownian Dynamics approach and has hardly been explored in the literature [41,78,84,101,127,135,140,169,171]. One difficulty arises from the degeneracy, and the resulting strong singularities in the equation of motion, attached to the commonly used rotational coordinate systems, such as the Euler angles [74].…”