Potential energy between two atoms

Question

Question: The potential energy between two atoms can be represented as shown below:

V = - (A/r) + (B/r¹⁰)

Where A and B are constants and r is the inter atomic separation distance. Plot the potential energy verses distance relationships for these atoms when A =  8 x 10^-30 J.m and B = 5 x 10^-119 J.m¹⁰. Find out the coefficient of thermal expansion (in m/m.K) for the material over the given temperature ranges:

a)  0^oK to 0^oC,
b)  0^oC to 820^oC.

Suppose that thermal energy of the system is 3kT/2 where k is Boltzman’s constant k = 1.381 x 10^-23 J/K.

Question: Gallium arsenide (GaAs) has the zinc blende structure. The gallium atoms are in FCC packing and the arsenic atoms occupy half the tetrahedral sites. Compute the density of Gallium arsenide (GaAs) by using the given data.

         Covalent Radius    Atomic Mass
 Ga    1.26 Ångstroms     69.7 g/mole
 As    1.19 Ångstroms     74.9 g/mole

Avogadro’s number (NAv) is 6.02 x 10²³ atoms per mole.

Question: Using the phase diagram below for the copper-silver system, find out:

i) The phases present

ii) The composition (wt % Cu) of those phases and

iii) The amount (wt %) of each phase for:

a) Copper-silver alloy (70 wt % copper) at 900 ^oC 
b) Copper-silver alloy (70 wt % copper) at 600 ^oC 
c) Copper-silver alloy (5 wt % copper) at 800 ^oC