| In this paper, absorb-hydrogen principle of hydrogen storage alloys and the functions of substitute element in hydrogen storage alloys have been investigated. Content as follows:The synthetical effects of rare earth compositions on texture growth properties in hydrogen storage alloys are analyzed by Partial Least Square(PLS) method, and some criteria for preferred orientation of alloy crystal faces are obtained. The electronic structures of LaNi5, Mg2Ni, LaNi4M(M=Al, Co,Cu, Mn) and these hydrides which were applied to analyze the bonding styles between hydrogen and alloying elements in hydrogen storage alloy and roles of hydride forming and non-forming elements, were investigated by the SCC-DV-Xα (Self-Consistent-Charge Discrete Variational Xα ) method; in addition to, the functions of substitute element in hydrogen storage alloys are also analyzed. These results show that:1. Nd is the most important element effecting the (101) + (201) crystal faces for parallel to columnar crystal and Pr is the most important element effecting the (200) + (110) crystal face for perpendicular to columnar crystal.2. In the LaNi5 hydrides, It was found that the covalent bond is formed by Ni4p orbit hybriding with H1s orbit, and the delocalized bond which is weaken when hydride is formed, is formed among Ni atoms and La atoms. The a axis of LaNi5 unit cell can been changed easier than c axis when hydrogen atom was absorbed.3. In the Mg2NiH4, the strong bond which is formed by Ni atoms with H atoms, is the main reason that MgiNi alloy need high temperature when hydrogen atom was release. In AB5, A2B type hydrogen storage alloys, hydrogen is apt to enter into the crystal lattice place which surround the endothermic elements, so the functions of endothermic elements is enforce the absorbability towards hydrogen. AB5 and A2B type hydrogen storage alloys all appears the phenomenon thatA-B bond is weaken after hydrogen atom was absorbed, it result in the lower performance ofalloy.4. In LaNi4M alloy, the charges number of outer orbits in substitute element were related to theequilibrium plateau pressure, and they have the same change trend. The 4p orbit in Ni (1) atomappear bond peak in the lower energy region, which is a mainly character that decreases theequilibrium plateau pressure. |
