Molecular Dynamics of a Crystal. 



145 



assemblage (I.), and also for the diatomic- assemblage (II.) . 

 The abscissa (a?) of each diagram, reckoned from a zero out- 

 side the diagram on the left, represents the distance between 

 centres of two atoms : the ordinates (y) represent the 

 work required to separate them from this distance to oo . 



Hence — ~r represents the mutual attraction at distance x. 



ax 



This we see by each curve is — x> (infinite repulsion) at 

 distance l'O, which means that the atom is an ideal hard ball 

 of diameter 10. For distances increasing from l'O the force 

 is repulsive as far as 1*61 in curve 1, and 1*55 in curve 2. 

 At these distances the mutual force is zero ; and at greater 



Fig. 4. 















m" 





/ \ 



fu-fcrJss. I. j 





















i-i 1/ 



y^uf:rAss.JJ. \ \ 





•8 ■ 



? V0 





71 '' 2 



•3 1-4- li 1-6 1-7 



1-8 



Law of Force according- to Curve 1 . 



distances up to 1*8 in curve 1, and 1*9 in curve 2, the force 

 is attractive. The force is zero for all greater distances than 

 the last mentioned in the two examples respectively. Thus, 

 according to my old notation, we have £ = 1*61, 1 = 1*8 in 

 curve 1 : and £=1*55, 1=1*9 in curve 2. The distances for 

 maximum attractive force (as shown by the points of inflection 

 of the two curves) are 1*68 for curve 1, and 1*76 for curve 2. 



According to our notation of § 4 we have ?/ = <£(D), if 

 a?=D in each curve. 



§ 15. The two formulas (7), § 12, are represented in fig. 4 

 for curve 1. and in fig. 5 for curve 2 ; with ,/' = A. for Ass. I. 

 and <r = *G13A. for Ass. II. In each diagram the abscissa, x. 



I'ldl. Mag. S. G. Vol. 4. Xo. 19. July 1902. L 



