questions about CPMD

1. When should I use NOSE MASSIVE?

For a simulation of a molecule in the gas phase the use of the MASSIVE thermostat is strongly recommended. In this context, massive does not refer to a more 'strict' or 'powerful' thermostat, but to a separate thermostat chain for each degree of freedom, i.e. massive referes to the total number of thermostats. This way a proper sampling of phase space is ensured, even if the various vibrational modes of the molecule(s) are only weakly coupled to the heat bath.

2. cpmd的几个问题。
   （1） symmetry 0 : ISOLATED system in a cubic/orthorhombic box with ISOLATED MOLECULE option activated.

cpmd _always_ uses periodic boundary conditions,
symmetry defines the shape of your supercell. SYMMETRY 0 is
a special case, where the effect of the periodic images ( In a box that is too small, a macromolecule may interact with its own image in a neighboring box, which is functionally equivalent to a molecule's "head" interacting with its own "tail". This produces highly unphysical dynamics in most macromolecules, ) is cancelled out, but for that to work correctly, there must not be any electron

density close to the borders of your supercell, so PBC or not
is no problem there.

           模拟结果和 
           symmetry 1: Simple CUBIC 
           or
           The ISOLATED MOLECULE keyword has only an effect on the calculation of the degrees of
freedom (3N-6 vs. 3N-3 for periodic systems).
           有何不同？？
           center molecule
           The main purpose of this is to center the molecule (center
of mass) in the box. This is needed for the HOCKNEY Poisson solver. This solver gives wrong
results if the charge density is not centered in the computational box.
     （2）包括GAUSSIAN， 这些软件是如何放置分子的？在CPMD里，就是按Cartesian坐标放的吗？怎么保证他们在同一个盒子
            里？
     （3）使用不同的虚拟电子质量和时间间隔究竟有何不同？
      （4）虚拟电子和原子核（EOF AND NOF）的耦合，热原子到虚拟冷电子的耦合究竟和真实的电子原子核耦合是一回事情吗？后者的BOA被打破和虚拟冷电子大量吸收原子核能量是一回事情吗？？