C Jan Labanowski, Aug 13, 1992
C This "program" calculates geometrical parameters of the methyl group rotor
C suitable for constructing Zmatrix
C The experimental data from microwave spectroscopy for CH3something
C are frequently given as a CH bond lengths and HCH angle for
C a equilateral methyl piramid (idealized), and the deviation of the
C the Csomething bond from the rotation axis of the CH3 (so called
C methyl group tilt). These data have to be converted to other parameters
C to be used in construction of the Zmatrix for the molecule.
C
C Input:
C d = CH bond length and theta = angle HCH
C
C Output:
C a = distance H....H (the side of the equilateral triangle formed by 3 H's)
C h = the height of the equilateral triangle formed by 3 H atoms
C v = height of the isosceles HCH
C alpha = angle between the CH bond and the height of the CH3 pyramid
C Hp = the height of the pyramid formed by CH3
C beta = angle between height of the HCH isosceles (v) and the
C height of pyramid (Hp)
C Sorry for FORTRAN ugliness, but it is a translation of the C original
PROGRAM METHYL
DOUBLE PRECISION d, theta, alpha, h, Hp, a, v, deg, beta
WRITE(*,*)
1 ' Enter CH bond length and HCH angle (in deg):'
READ(*,*)d,theta
WRITE(*,*)
deg = 3.1415926536D0/180.0D0
a = 2.0D0*d*dsin(0.5D0*theta*deg)
v = d*dcos(0.5D0*theta*deg)
h = 0.5D0*a*dsqrt(3.0D0)
Hp = dsqrt(d*d  a*a/3.0D0)
alpha = dacos(Hp/d)/deg
beta = dacos(Hp/v)/deg
100 FORMAT(1X,A,F10.5)
WRITE(*,100) 'CH bond length = ', d
WRITE(*,100) 'HCH angle = ', theta
WRITE(*,100) 'Height of the HCH isosceles =', v
WRITE(*,100) 'H....H distance = ', a
WRITE(*,100) 'Height of pyramid base (h)= ', h
h = 2.0D0*h/3.0D0
WRITE(*,100) '2/3*h = ',h
WRITE(*,100) 'Angle between CH bond and pyramid height = ',
1 alpha
WRITE(*,100) 'Pyramid height = ', Hp
WRITE(*,100) 'Angle between wall height and pyramid height =',
1 beta
STOP
END
