[ESPResSo-devel] error in dawaanr interaction

[Markus Gusenbauer]

Hi,

I am wondering if the equation for the dawaanr (dipole-dipole) 
interaction implemented in ESPResSo is correct 
(magnetic_non_p3m_methods.c).

According to the following papers the force equation in the code is 
missing the term µ0/(4 pi):

E. P. Furlani, Permanent magnet and electromechanical devices: 
materials, analysis, and applications, Academic Press, 2001.

S. Melle, O. G. Calder ́n, M. A. Rubio, G. G. Fuller, Microstructure 
evolution in magnetorheological suspensions governed by
mason number, Physical Review E 68 (4) (2003) 041503.

S. Krishnamurthy, A. Yadav, P. E. Phelan, R. Calhoun, A. K.Vuppu, A. A. 
Garcia, M. A. Hayes, Dynamics of rotating paramagnetic particle chains 
simulated by particle dynamics, stokesian dynamics and lattice boltzmann 
methods, Microfluidics and Nanofluidics 5 (1) (2007) 33–41.


As µ0 = 4 pi 10⁻⁷ we can cancel 4 pi, but still 10⁻⁷ is absent. Maybe I 
miss something important. Can anyone clarify this issue? Thanks!

Markus