enddo
return
end
-C-----------------------------------------------------------------------------
- subroutine refsys(i2,i3,i4,e1,e2,e3,fail)
- implicit real*8 (a-h,o-z)
- include 'DIMENSIONS'
-c this subroutine calculates unity vectors of a local reference system
-c defined by atoms (i2), (i3), and (i4). the x axis is the axis from
-c atom (i3) to atom (i2), and the xy plane is the plane defined by atoms
-c (i2), (i3), and (i4). z axis is directed according to the sign of the
-c vector product (i3)-(i2) and (i3)-(i4). sets fail to .true. if atoms
-c (i2) and (i3) or (i3) and (i4) coincide or atoms (i2), (i3), and (i4)
-c form a linear fragment. returns vectors e1, e2, and e3.
- logical fail
- double precision e1(3),e2(3),e3(3)
- double precision u(3),z(3)
- include "COMMON.CHAIN"
- data coinc /1.0d-13/,align /1.0d-13/
- fail=.false.
- s1=0.0d0
- s2=0.0d0
- do 1 i=1,3
- zi=c(i,i2)-c(i,i3)
- ui=c(i,i4)-c(i,i3)
- s1=s1+zi*zi
- s2=s2+ui*ui
- z(i)=zi
- 1 u(i)=ui
- s1=sqrt(s1)
- s2=sqrt(s2)
- if (s1.gt.coinc) goto 2
- write (iout,1000) i2,i3,i1
- fail=.true.
- return
- 2 if (s2.gt.coinc) goto 4
- write(iout,1000) i3,i4,i1
- fail=.true.
- return
- 4 s1=1.0/s1
- s2=1.0/s2
- v1=z(2)*u(3)-z(3)*u(2)
- v2=z(3)*u(1)-z(1)*u(3)
- v3=z(1)*u(2)-z(2)*u(1)
- anorm=sqrt(v1*v1+v2*v2+v3*v3)
- if (anorm.gt.align) goto 6
- write (iout,1010) i2,i3,i4,i1
- fail=.true.
- return
- 6 anorm=1.0/anorm
- e3(1)=v1*anorm
- e3(2)=v2*anorm
- e3(3)=v3*anorm
- e1(1)=z(1)*s1
- e1(2)=z(2)*s1
- e1(3)=z(3)*s1
- e2(1)=e1(3)*e3(2)-e1(2)*e3(3)
- e2(2)=e1(1)*e3(3)-e1(3)*e3(1)
- e2(3)=e1(2)*e3(1)-e1(1)*e3(2)
- 1000 format (/1x,' * * * error - atoms',i4,' and',i4,' coincide.')
- 1010 format (/1x,' * * * error - atoms',2(i4,2h, ),i4,' form a linear')
- return
- end
-