how to convert matrix into positve definate ?

http://www.mathworks.in/matlabcentral/answers/6057

x = fmincon(@(x) objfun(x,Abad,indices,M), x0,[],[],[],[],-2,2,... @(x) confun(x,Abad,indices,M),opts);

explanation of x?

As above address u can convert the A0 matrix into positive definite matrix. how to convert following matrix? same is not working for d_2.

d_2=[ 8.7837 11.3869 + 0.9422i zeros(1,6); 11.3869 - 0.9422i 16.6414 zeros(1,6); 0 0 4.3551 5.3644 + 1.3811i zeros(1,4); 0 0 5.3644 - 1.3811i 8.0323 zeros(1,4); zeros(4,8)]