Chimie Théorique » Opt'n Path

!-----------------------------------------------------------------------

      subroutine rotation_matrix(q, U)

!-----------------------------------------------------------------------

! This subroutine constructs rotation matrix U from quaternion q.

!-----------------------------------------------------------------------

! This subroutine calculates RMSD using quaternions.

! It is based on the F90 routine bu E. Coutsias

! http://www.math.unm.edu/~vageli/homepage.html

! I (PFL) have just translated it, and I have changed the diagonalization

! subroutine.

! I also made some changes to make it suitable for Cart package.

!----------------------------------------------------------------------

!----------------------------------------------------------------------

! Copyright (C) 2004, 2005 Chaok Seok, Evangelos Coutsias and Ken Dill

!      UCSF, Univeristy of New Mexico, Seoul National University

! Witten by Chaok Seok and Evangelos Coutsias 2004.

! This library is free software; you can redistribute it and/or

! modify it under the terms of the GNU Lesser General Public

! License as published by the Free Software Foundation; either

! version 2.1 of the License, or (at your option) any later version.

!

! This library is distributed in the hope that it will be useful,

! but WITHOUT ANY WARRANTY; without even the implied warranty of

! MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU

! Lesser General Public License for more details.

!

! You should have received a copy of the GNU Lesser General Public

! License along with this library; if not, write to the Free Software

! Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301  USA

!----------------------------------------------------------------------------

        Use VarTypes

      real(KREAL) :: q(4)

      real(KREAL) :: U(3,3)

      real(KREAL) :: q0,q1,q2,q3,b0,b1,b2,b3,q00,q01,q02,q03

      REAL(KREAL) :: q11,q12,q13,q22,q23,q33

      q0 = q(1)

      q1 = q(2)

      q2 = q(3)

      q3 = q(4)

      b0 = 2.0d0*q0

      b1 = 2.0d0*q1

      b2 = 2.0d0*q2

      b3 = 2.0d0*q3

      q00 = b0*q0-1.0d0

      q01 = b0*q1

      q02 = b0*q2

      q03 = b0*q3

      q11 = b1*q1

      q12 = b1*q2

      q13 = b1*q3

      q22 = b2*q2

      q23 = b2*q3

      q33 = b3*q3

      U(1,1) = q00+q11

      U(1,2) = q12-q03

      U(1,3) = q13+q02

      U(2,1) = q12+q03

      U(2,2) = q00+q22

      U(2,3) = q23-q01

      U(3,1) = q13-q02

      U(3,2) = q23+q01

      U(3,3) = q00+q33

      end