+C xj=c(1,nres+j)-xi
+C yj=c(2,nres+j)-yi
+C zj=c(3,nres+j)-zi
+ xj=c(1,nres+j)
+ yj=c(2,nres+j)
+ zj=c(3,nres+j)
+ xj=mod(xj,boxxsize)
+ if (xj.lt.0) xj=xj+boxxsize
+ yj=mod(yj,boxysize)
+ if (yj.lt.0) yj=yj+boxysize
+ zj=mod(zj,boxzsize)
+ if (zj.lt.0) zj=zj+boxzsize
+ if ((zj.gt.bordlipbot)
+ &.and.(zj.lt.bordliptop)) then
+C the energy transfer exist
+ if (zj.lt.buflipbot) then
+C what fraction I am in
+ fracinbuf=1.0d0-
+ & ((positi-bordlipbot)/lipbufthick)
+C lipbufthick is thickenes of lipid buffore
+ sslipj=sscalelip(fracinbuf)
+ ssgradlipj=-sscagradlip(fracinbuf)/lipbufthick
+ elseif (zi.gt.bufliptop) then
+ fracinbuf=1.0d0-((bordliptop-positi)/lipbufthick)
+ sslipj=sscalelip(fracinbuf)
+ ssgradlipj=sscagradlip(fracinbuf)/lipbufthick
+ else
+ sslipj=1.0d0
+ ssgradlipj=0.0
+ endif
+ else
+ sslipj=0.0d0
+ ssgradlipj=0.0
+ endif
+ aa=aa_lip(itypi,itypj)*(sslipi+sslipj)/2.0d0
+ & +aa_aq(itypi,itypj)*(2.0d0-sslipi+sslipj)/2.0d0
+ bb=bb_lip(itypi,itypj)*(sslipi+sslipj)/2.0d0
+ & +bb_aq(itypi,itypj)*(2.0d0-sslipi+sslipj)/2.0d0
+
+ dist_init=(xj-xi)**2+(yj-yi)**2+(zj-zi)**2
+ xj_safe=xj
+ yj_safe=yj
+ zj_safe=zj
+ subchap=0
+ do xshift=-1,1
+ do yshift=-1,1
+ do zshift=-1,1
+ xj=xj_safe+xshift*boxxsize
+ yj=yj_safe+yshift*boxysize
+ zj=zj_safe+zshift*boxzsize
+ dist_temp=(xj-xi)**2+(yj-yi)**2+(zj-zi)**2
+ if(dist_temp.lt.dist_init) then
+ dist_init=dist_temp
+ xj_temp=xj
+ yj_temp=yj
+ zj_temp=zj
+ subchap=1
+ endif
+ enddo
+ enddo
+ enddo
+ if (subchap.eq.1) then
+ xj=xj_temp-xi
+ yj=yj_temp-yi
+ zj=zj_temp-zi
+ else
+ xj=xj_safe-xi
+ yj=yj_safe-yi
+ zj=zj_safe-zi
+ endif
+