Chemical differences between K and Na in alkali cobaltates

نویسندگان

  • K.-W. Lee
  • W. E. Pickett
چکیده

KxCoO2 shares many similarities with NaxCoO2, as well as some important differences no hydrationinduced superconductivity has been reported . At Tc2=20 K, K0.5CoO2 becomes an insulator with a tiny optical gap, as happens in Na0.5CoO2 at 52 K. This similarity, with a known common structure, enables direct comparisons to be made. Using the K-zigzag structure recently reported and the local density approximation, we compare and contrast these cobaltates at x=0.5. Although the electronic structures are quite similar as expected, substantial differences are observed near the Fermi level. These differences are found to be attributable mostly to the chemical rather than the structural difference. Although Na is normally considered to be fully ionic, K has a somewhat more highly ionic character than does Na in these cobaltates.

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

منابع مشابه

Topological Analysis of Theoretical Charge Density of Alkali Metal Cations (LC, Na+, le)ICrown Ether (18e6) Complexes

The DO1(18c6)fi (MwLi. Na. K and I 8c6=18-crown-6) complexes have been chosen as the model systems toinvestigate the nature of chemical bonds between alkali metal cations and large mffitidentaie orgmnic ligands.The B3LYP/6-3I+G(d,p) level of calculation has been used for obtaining equilibrium geernetnes and p(r)functions (electron density distributions). By the aid of fundamental physical theor...

متن کامل

Optimizing the Properties of Metakaolin-based (Na, K)-Geopolymer Using Taguchi Design Method

Geopolymer paste is an innovative construction material which shall be produced by chemical action of inorganic molecules. It is a more environmentally friendly alternative to conventional Portland cement which is abundantly available worldwide. In this study, the influence of different alkaline activators (Na and K) on the mechanical and thermal behaviors of metakaolin-based geopolymer was inv...

متن کامل

Geochemical Aspects of Na-Metasomatism in Sargaz Granitic Intrusion (South of Kerman Province, Iran)

The Sargaz granitic intrusion has been emplaced in Sargaz ophiolitic suite, south-east of Sanandaj-Sirjan metamorphic zone, south of Kerman province. The central part of the intrusive body contains pinkish coarse-grained granite, but the fractured northern part, neighboring Chah-Mazraeh fault, has been subjected to pervasive Na-metasomatism and related subsolidus reactions. In the northern alte...

متن کامل

ON THE COMPLEXING ABILITY OF ERIOCHROME BLACK T AS A METALLOCHROMIC INDICATOR FOR SOME ALKALI AND ALKALINE EARTH CATIONS IN ACETONE AND DIMETHYLSULPHOXIDE SOLUTIONS

The interaction between eriochrome black T and Li , Na , K ,Mg and Ca ions in acetone and dimethylsulphoxide solutions has been investigated spectrophotometrically. The formation constants of the resulting 1 : 1 complexes were determined and found to decrease in the order Mg >Ca >Li >K >Na in both solvents used. There is an inverse relationship between the stabilities of the complexes...

متن کامل

Experimental and theoretical determination of adsorption heats of CO(2) over alkali metal exchanged ferrierites with different Si/Al ratio.

The adsorption of CO(2) in Li-, Na-, and K-FER was investigated by a combination of volumetric adsorption experiments, FTIR spectroscopy, and density functional theory. Experimental isosteric heats of CO(2), Q(st), depend significantly on the cation size, cation concentration, and on the amount of adsorbed CO(2). The differences observed in experimentally determined isosteric heats were interpr...

متن کامل

ذخیره در منابع من


  با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید

برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید

ثبت نام

اگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید

عنوان ژورنال:

دوره   شماره 

صفحات  -

تاریخ انتشار 2007