Classical molecular dynamics approach for the orientation of diatomic molecules as a model of the large molecules

The preliminary calculation for the possibility of the orientation of large molecules with electric field was carried out. The rotational motion of large molecules such as proteins would be changed continuously because of their very small rotational constant. Then, the useful information about the molecular orientation of large molecules using electric field would be obtained with classical molecular dynamics. A diatomic molecule was used as the simplest model of large molecules. Further simplifications were applied; (1) (quasi-)rigid rotator was calculated by setting very large force constant; (2) initial velocities were set to 0 for all trajectory calculation; (3) the motions were limited to only one plane. Our results show that from -π/2 rad to π/2 rad of initial polar angle, considerably high field-free temporal orientation is achieved even when only one short pulse electric field are applied. (author)