 The underling structure of this asymmetrical heat flow is the hydrogen bond of normal length (~2.85 {\AA}) , that can act as a thermal diode.
<clarity>  The underling structure of this asymmetrical heat flow is the hydrogen bond of normal length (~2.85 {\AA}) , that can act as a thermal diode.
 The underling structure of this asymmetrical heat flow is the hydrogen bond of normal length (~2.85 {\AA}) that acted as a thermal diode.