Anomalies of liquid water at low temperature due to two types of hydrogen bonds

It is believed that water anomalies are related to the hydrogen bonds between water molecules, but the relationship still remains a challenge. Here, by introducing two types of hydrogen bond--strong and weak, we successfully reproduce many liquid water anomalies, particularly the thermodynamic anomalies at supercooled temperature. We find that the exchange of strong and weak H bonds, which enhance the competition between the open and collapsed structures of liquid water, might be the key to those anomalies of supercooled liquid water. Our study is helpful in understanding the hydrogen bond structure in liquid water.