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LITlib - Excel Power Functions Pack
 
Add-in for Excel that adds additional cell functions to Excel.

litLIB Help - MolCenterOfMass function
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Chemistry - MolCenterOfMass

Syntax:
= MolCenterOfMass(AtomsXYZ)

Description:
Returns the center of mass (centre of mass ; c.o.m.) of a set of atoms. To determine the center of mass the atomic weight of the atoms are used.

AtomsXYZ: The cells that contain in column 1 the atomic symbol and in columns 2 to 4 the XYZ coordinates.

MolCenterOfMass is an array function. Select 3 cells (1 row, 3 columns) and enter the formula. Then press CTRL+SHIFT+ENTER to create the array formula.

Example:
Calculate the center of mass of H2O

     A     B     C     D
1   O     0     0     0
2   H     1     1     1
3   H     1   -1     1

Select cells A5:D5. Enter the following formula
=CenterOfMass(B1:D3)
Press CTRL+SHIFT+ENTER

Result:
     A     B     C     D
1   O     0     0     0
2   H     1     1     1
3   H     1   -1     1
4
5        0.119  0   0

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