Array factor calculation problem

Hi there, I am curious that Array factor and total gain of array is it the same or not?
if it is not the same how to calculate it.

Thank you for all helps

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One more thing, if the separation distance of antenna is 0.65 wavelength, what would be the phase difference between them?

Array factor and gain are different. The Array Factor is a function of the positions of the antennas in the array and the weights used.
for calculation chk this link http://www.antenna-theory.com/arrays/arrayfactor.php
The phase difference will be dependent on angle of incidence or transmitting angle..
phase_diff = 2πdsinθ/λ