Polar scatter plot and histogram distributions for halogen bonds. (

*a*) Polar scatter plot relative to Θ

_{1} and the normalized halogen (

*X*) to oxygen distances (

*R*_{X}_{···O}, where

*R*_{X}_{···O} ≤

*R*_{vdW}) are plotted for

*X*&

Cl (green circles),

*X*Br (red triangles), and

*X*I (cyan squares). Both the

*x* and

*y* axes of the plot represent

*R*_{X}_{···O}, with the

*y* axis aligned along the C

*X* bond (180°) and the

*x* axis perpendicular to the C

*X* bond (90°). The shaded region from 90° to 120° indicates the Θ

_{1} angles that were excluded from our data set. (

*b*) Histogram distribution of Θ

_{1} angles. The number of short

*X*···O interactions to chlorine (green), bromine (red), and iodine (cyan) halogen atoms, and their sum (gray) are counted and placed into 5° bins of Θ

_{1} angle and plotted as a 3D histogram. (

*c*) Histogram distribution of Θ

_{2} angles. This plot is similar to

*b*, except the interactions are placed into 10° bins of Θ

_{2}. (

*d)* Histogram distribution of the dihedral angle Ψ calculated for short halogen bonds involving the O

C group of the peptide backbone.

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