wbfan95 / boncar

A Fortran code of converting bond lengths to Cartersian coordinates.

bonCar

A Fortran code of converting bond lengths to Cartersian coordinates.

Introduction

Converting Cartesian coordinates to bond lengths is simpler than the inverse convert. The bond-Cart transformation is intuitively straight-forward but hard to realize.

Difficulty

The first difficulty I met is how to solve the fourth coordinates if we knew three coordinates and three lengths, which confused me for many days. Actually this is a common transformation in GIS called trilateration.

The second difficulty I didn't solve is how to deal with the colinear condition. If three or more atoms are in one line, there will not be a solution for the fourth point, although the condition is rare.

Converting Procedure

1. The first atom was placed at the origin.
2. The second atom was placed at the x axis.
3. The third atom was placed at the xOy plane.
4. The fourth was placed at the positive half Z axis.
5. Then other atoms was solved one by one.

Usage

The core subroutine is bonCar. The number of bond lengths, bond lengths, the number of atoms are required.

Intel Fortran Compiler is needed. No more prerequisite.

1. Clone this repository.
2. make