CPMD方法
Car-Parrinello Molecular Dynamics（簡稱CPMD）是一種第一原理分子動力學（ab initio molecular dynamics）方法，該方法利用了贗勢、平面波基矢和密度泛函理論（DFT）對原子（分子）間作用力進行計算，
In contrast to Born–Oppenheimer molecular dynamicswherein the nuclear (ions) degree of freedom are propagated using ionicforces which are calculated at each iteration by approximately solvingthe electronic problem with conventional matrix diagonalizationmethods, the Car–Parrinello method explicitly introduces the electronicdegrees of freedom as (fictitious) dynamical variables, writing anextended Lagrangian for the system which leads to a system of coupled equations of motionfor both ions and electrons. In this way an explicit electronicminimization at each time step, as done in Born-Oppenheimer MD, is notneeded: after an initial standard electronic minimization, thefictitious dynamics of the electrons keeps them on the electronic ground statecorresponding to each new ionic configuration visited along thedynamics, thus yielding accurate ionic forces. In order to maintainthis adiabaticity condition,it is necessary that the fictitious mass of the electrons is chosensmall enough to avoid a significant energy transfer from the ionic tothe electronic degrees of freedom. This small fictitious mass in turnrequires that the equations of motion are integrated using a smallertime step than the one (1–10 fs) commonly used in Born–Oppenheimermolecular dynamics.
