Ab initio study of the one-dimensional H-bonded ferroelectric CsH2 PO4

P. N. ABUFAGER; J. LASAVE; S. KOVAL

PHYSICAL REVIEW B

AMER PHYSICAL SOC

Lugar: New York; Año: 2016 vol. 93 p. 134112 - 134112

1098-0121

We studied the microscopic mechanism of the paraelectric-ferroelectric (PE-FE) phase transition of CsH2 PO4(CDP) by means of first-principles electronic structure calculations. The calculated structural parameters in thePE and FE phases as well as the total spontaneous polarization Ps obtained with the Berry phase formalism forCDP are in good agreement with experiments. The main contribution to Ps originates from a large yx componentof the calculated Born effective-charge tensor for the disordered protons. Moreover, this component is ≈2.7 timeslarger than the zx component of the proton effective-charge tensor relevant to the polarization in the H-bondedFE KH2 PO4 (KDP). This is the main feature that compensates the different number of protons per formula unitinvolved in the phase transitions for CDP and KDP to give close values for their measured Ps . Correlationsamong protons and heavy atoms along chains in the b direction lead to larger instabilities for the global and localFE distortions in CDP and its deuterated counterpart DCDP. We conclude that the tunneling particle is a dressedproton (deuteron) in agreement with experiments and with recent ab initio results for KDP.