dJ_FN_SI_Asym.m

function dJ=dJ_FN_SI_Asym(F, phi)
dJ=zeros(1,length(F));
%F = -1*F;  %we defined field in a certain direction, so we use F=F
for i=1:length(F)
    if F(i)>0
        a_const = 1.541534e-6;
        b_const = 6.83089;

        f = 1.43996453529595*F(i)/phi.^2;
        v_f = 1;%1 - f + 1/6.*f.*log(abs(f));%simplified FN v_f=1
        alpha = a_const/phi;
        beta = v_f*b_const*phi.^(3/2);
        dJ(i) = (2*a_const/phi*F(i) + a_const*v_f*b_const*phi.^(1/2))*exp(-v_f*b_const*phi.^(3/2)/F(i));
    else
        dJ(i)=0;
    end
end