how draw graph of the einstein model of a solid gives the specific
heat as Cv = 3R[ e^(hv/kt)/(e^(hv/kt) -1)^2 *(hv/kt)^2]

Draw a graph of what? You've only given an equation, and as such I
could say that plotting x against y gives a straight line.

Presumably however you what to know how Cv varies with t (as
everything else in that equation is a constant).

A few pointers... When t is small, is Cv large, small, 0, infinite?
And when it's large?

Stephan

#!/usr/bin/perl -w

# dream up your own numbers and check I've interpreted
# the operations to your liking

$R=1.0;
$hv=1.0e-16;
$k=1.38e-19;

# Cv = 3R[ e^(hv/kt)/(e^(hv/kt) -1)^2 *(hv/kt)^2]
for($t=25; $t<900 ;$t +=25) {

    $hvokt=$hv/($k * $t);
    $ex=exp $hvokt;
    $minusone=$ex-1;

    next if (abs($minusone) < 0.00000000001);
    $cv= $ex * ($hvokt * $hvokt) / ($minusone * $minusone);
    $cv *= 3;
    $cv *= $R;

    printf("%8.4f %8.4f\n",$t, $cv);
}


produces

 25.0000   0.0000
 50.0000   0.0003
 75.0000   0.0178
100.0000   0.1124
125.0000   0.3080
150.0000   0.5677
175.0000   0.8451
200.0000   1.1099
225.0000   1.3480
250.0000   1.5556
275.0000   1.7336
300.0000   1.8853
325.0000   2.0143
350.0000   2.1241
375.0000   2.2180
400.0000   2.2985
425.0000   2.3678
450.0000   2.4279
475.0000   2.4801
500.0000   2.5258
525.0000   2.5659
550.0000   2.6013
575.0000   2.6326
600.0000   2.6605
625.0000   2.6854
650.0000   2.7077
675.0000   2.7278
700.0000   2.7459
725.0000   2.7622
750.0000   2.7771
775.0000   2.7907
800.0000   2.8030
825.0000   2.8143
850.0000   2.8247
875.0000   2.8343

which can be plotted in any decent graphing package - or even MS Excel.