报告题目：Ion-orbital interactions in Car-Parinnello molecular dynamics: implications for calculations of dynamical quantities
报告人：Kang Hway Chuan 教授
Department of ChemistryNational University of Singapore
报告时间：2012年6月20日（星期三）下午 14:00 ---15:00
报告地点：独墅湖校区907号楼1445室
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报告摘要：
In this talk we will discuss our investigations of ion-orbital interaction in Car-Parinnello molecular dynamics (CPMD). One of the key ideas in CPMD is the introduction of an orbital mass in order to map the electronic relaxation to fictitious classical dynamical degrees of freedom. This makes it possible to simultaneously simulate the motion of the ions and relax the electronic structure. It also introduces an fictitious interaction between the ions and the orbital modes which go to zero in the adiabatic limit at zero orbital mass. We show analytically that this interaction can be described by linearly coupled oscillators when the system is sufficiently close to the ground state. This leads to ionic vibrational modes with frequency wM that depends upon the ionic mass M and the orbital mass m as in the limit of zero m/M; wM0 is the Born-Oppenheimer ionic frequency and the constant C depends upon the ion-orbital coupling force constants. This analysis provides new insight on the orbital mass dependence of the dynamics, and suggests a rigorous method of obtaining accurate ionic vibrational frequency using CPMD. We verify our analytical results with numerical simulations for N2, Sn2, and H/Si(100)-(2×1). Since the CPMD method is very attractive for simulating large systems of biological interest we also discuss some implications for hydrogen-bonded systems. We consider the vibrational frequencies of the NH3-HCl dimer, and also the self-diffusion coefficient and the hydrogen-bond lifetime in liquid water. Our results show that it is not trivial to extract accurate dynamical quantities from CPMD.
博彩平台
2012-6-18
