Lecture05

Important features of the force acting between as

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Unformatted text preview: t features of the force acting between (as modeled with the Lennard-Jones 1 Potential) two particles are revealed by applying the relationship 0.8 listed in (1) above to the graph. 0.6 ! The force is strongly repulsive when the two 0.4 0.2 particles are separated by a distance less than that 0 corresponding to the minimum of the potential. 0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 2.6 2.8 3 -0.2 ! The force is attractive when the particle separation -0.4 is greater than that corresponding to the minimum -0.6 of the potential. -0.8 -1 ! The attractive force approaches zero as the -1.2 separation becomes greater than a couple of particle distance between centers of atoms, r diameters. (in units of particle diameter, ! ) The particular curve shown in this graph is known as the Lennard-Jones potential and is an excellent approximation for noble gas atoms. However, all pair-wise potential energies for neutral particles (including molecules) have this general shape with these features. kinetic and pair-wise potential energies. 5) The interactions of one particle in a liquid or solid with all of its neighbors add together to form one threedimensional potential energy with a minimum that defines the equilibrium position of that particle (where the net force due to all of the pair-wise interactions is zero). We refer to this potential as the single-particle potential energy to distinguish it from the pair-wise potential energy. 6) Each...
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This note was uploaded on 05/30/2009 for the course PHY 7A taught by Professor Pardini during the Fall '08 term at UC Davis.

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