Measuring

# 2.1.7 Measuring Tools

Ghemical can measure the distance between atoms, the angle formed by three atoms and the dihedral angle formed by four atoms. In molecular mechanics models ghemical will can also measure an approximate charge on an atom.

## Measuring Charges

To find the approximate charge of an atom, click on the Measure button on the left toolbar. Now left click on the atom you want to measure the charge of. The approximate charge will be displayed in the log box automatically. The output in the log box at the bottom of the window will look something like this:
`charge: -0.25`
Note this only applies to molecular mechanics models; in the current version it is not possible to measure charges in quantum mechanical models.

## Measuring Distances

To measure the distance between two atoms (such as a bond length), click on the Measure button on the left toolbar. Now left click on the atoms you want to measure the distance between. The color of the atoms selected for measurement will be changed to pink. The distance between the two atoms will automatically be displayed in the log box once the second atom is selected. The output in the log box will look something like this:
`distance: 0.150697 nm`
The atoms do not have to be bonded; the distance between any two atoms in a molecule can be measured.

## Measuring Angles

To measure the angle formed by three atoms, click on the measure button on the left toolbar. Now left click on the three atoms that form the angle you want to measure. The order that they are selected is important; the first edge of angle that is measured are the the line between the first and second atoms and the second edge is between the second and third atoms, making the second atom the central atom. When the third atom is selected, the angle is automatically displayed in the log box. The output in the log box will look something like this:
`angle: 109.471 deg`
As with distances, the atoms forming the angle to not have to bonded to each other.

## Measuring Torsions

To measure the torsion angle formed by four atoms click on the measure button on the left toolbar. Now select the four atoms for the torsion angle. The first three atoms selected will define a plane. The angle displayed is the angle between this plane and a line from the fourth atom to the second. The torsion angle is displayed in the log box as soon as the fourth angle is selected. The output in the log box will look something like this:
torsion: 120 deg

## Notes

Atoms that have been selected can be unselected by clicking on them again. All atoms are automatically unselected when a fourth atom is selected. There are toggle buttons on the top toolbar labeled "The distance measuring mode," "The angle measuring mode," and "The torsion measuring mode" In the current release these toggle buttons have no effect on the measuring tool.

Return to index