code: private void calculateTranslationalAxis(Matrix rotation, Atom translation) {
  		// set axis parallel to translation
  		rotationAxis = Calc.scale(translation, 1./Calc.amount(translation));
  
  		// position is undefined
  		rotationPos = null;
  
  		screwTranslation = translation;
  		otherTranslation = new AtomImpl();
  		otherTranslation.setCoords(new double[] {0,0,0});
  	}
docs: Handle cases with small angles of rotation
  @param rotation
  @param translation