subroutine ledouxc * * compute modified Ledoux B term to include composition gradient * effects in the Brunt-Vaisala frequency * This is the version that computes the B term in the core. * I vary both the C and O abundance at the C/O interface. * PAB 1 October 1991 * implicit double precision(a-h,o-z) * * has log T=t2, log Rho=u2, C abun.=xc2, O abun.=xo2, and log P=p2 * common/temp/s1,r1,s2,r2,b2,p2,t2,ea2,xc2,xo2,fca2,f2,q2,w2,c common/thermo/u2,up2,ut2,e2,ep2,et2,psi2,pg,o2,op2,ot2,fp,ft, 1 en2(5),fn,fcc,ce,ci,cif,w,nu * * ledoux term value * common/bldxc/bledc real*8 x(4) * * DEL is step size increment in composition * bledc = 0.0 del = 0.01 x(1) = 0.0 x(2) = 0.0 x(3) = xc2 x(4) = xo2 * * C/O interface * I am computing partial ln P/partial ln O here. * now to consider specific composition mixtures! * CASE 3: x(4) or x(3) is less than del (use a 3 point formula) * CASE 3.1: Nearly pure oxygen: Treat first point as pure O. * treat second point as C/O mixture * if(x(3).lt.del)then diff = 1.0-x(4) xone = x(4) - diff xc2 = 1.0 - xone xo2 = xone call istatco(p2,t2,1,.false.) dens1 = 10.**(u2) xtwo = 1.0 xc2 = 0.0 xo2 = xtwo call istatco(p2,t2,1,.false.) dens2 = 10.**(u2) xc2 = x(3) xo2 = x(4) bledc=(xo2/(2.*diff))*(dlog(dens2)-dlog(dens1)) return * * CASE 3.2: Nearly pure Carbon: Treat first point as pure C. * treat second point as C/O mixture * else if(x(4).lt.del)then diff = x(4) xone = 0.0 xc2 = 1.0 - xone xo2 = xone call istatco(p2,t2,1,.false.) dens1 = 10.**(u2) xtwo = x(4) + diff xc2 = 1.0 - xtwo xo2 = xtwo call istatco(p2,t2,1,.false.) dens2 = 10.**(u2) xc2 = x(3) xo2 = x(4) bledc=(xo2/(2.*diff))*(dlog(dens2)-dlog(dens1)) return endif * * CASE 2: We are not near 0 or 1 in composition * we can use 3-point differencing formula with impunity. * xone = x(4) - del xo2 = xone xc2 = 1.0 - xone call istatco(p2,t2,1,.false.) dens1 = 10.**(u2) xtwo = x(4) + del xo2 = xtwo xc2 = 1.0 - xtwo call istatco(p2,t2,1,.false.) dens2 = 10.**(u2) xc2 = x(3) xo2 = x(4) bledc=(xo2/(2.*del))*(dlog(dens2)-dlog(dens1)) return end ************************************************************************