Hi Kostya and others, >I am proposing to restart CP with finite ionic velocities and MOVING >orbitals. This is achieved by doing a couple of BO (CG) steps for >moving ions, with the fully converged wavefunctions for the last 2 >steps saved. This way CP will be restarted from the BO wavefunctions >which were moving with the ions and thus contain the full drag effect >(and only the drag effect!). > > I think this is identical to restarting CP with both ionic and >wavefunction velocities set to zero, only now they can be finite.
This is a very good idea! I have a further suggestion for developers: How about providing a means of rescaling the masses of the ions in the code, as Sandro Scandolo and I showed was necessary for the correct calculation of temperature, thermal pressure, and dynamical properties ? A large part of the dragging effect is a renormalization of the ionic masses by an amount dM. That means that temperature should be calculated as 3(N-1)kT = \sum (M+dM) v^2 A way to significantly improve dynamical properties and calculate the temperature more correctly is to evolve the ions using a mass of M-dM (i.e. acceleration = F/(M-dM) ), and then to calculate temperature with a mass of M. (dM can be calculated by minimizing errors in Car-Parrinello forces w.r.t. ground state forces....this could also be facilitated in the code.) It would be great if the code allowed you to input dM and have it do the rescaling, the calculation of temperature both with and without mass corrections (because away from the strongly-ionic limit the definition of temperature is less clear), and the calculation of the fictitious kinetic energy minus the dragging contribution. I used to have all this implemented in FPMD, but somehow it never made its way into the official version. Regards, Paul -- ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo Dr. Paul Tangney Theory of Nanostructured Materials Facility The Molecular Foundry Lawrence Berkeley National Lab. E-mail: PTTangney at lbl.gov 1 Cyclotron Road, Bldg 66 Phone: (510) 642-2635 Berkeley, CA 94720 Fax : (510) 643-9345 ooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooooo
