Preparation, thermal analysis, and crystal structure refinement of the quaternary alloy (CuIn)2NbTe5

The quaternary alloy (CuIn)2NbTe5 was synthesized by solid-state reaction using the melt and annealing technique. The thermal analysis shows that this compound melts at 1026 K. The present alloy is isotypic with Cu2FeIn2Se5 and crystallizes in the space group P2c (Nº 112), with unit cell parameters a = 6.1964(2) Å, c = 12.4761(4) Å, c/a = 2.01, V = 479.02(3) Å3. (CuIn)2NbTe5, belonging to the system (CuInSe2)1-x(FeSe)x with x= ⅓, is a new adamantane compound with a P-chalcopyrite structure. This structure is characterized by a double alternation of anions-cations layers according to the Te-Te : Nb-In-Nb-In : Cu-In-Cu-In : Te-Te sequence, along the 010 direction.

Which is bigger? An intriguing ‘double alternation’

The following three inequalities hold:The first inequality is trivial. The second one was proved without calculating aids in note [1], and the third along similar lines in note [2]. The author of note [2] also suggested an extension to the relation betweenHow best to continue the sequence of inequalities is not obvious and we return to that point shortly. Before doing so, we note that an interesting geralisation is to replace π by a variable x, and to determine the precise interval of x in which the regularity of the ‘alternation of inequality signs’ is maintained. We need no longer consider particular properties of π.

A Cognitive Maze

A cognitive maze was developed to study perceptual and conceptual processes in the discovery of relationships through inductive inference and flexible shifting of mental sets adaptive to changed problems. For example, the experimenter-tester presents a list of digits in consecutive pairs; subject-testee is asked to select one digit from each pair and tester answers “right” or “wrong” according to whether the choice agrees or disagrees with the hidden principle fixed for that particular problem. After reaching criterion, the principle is stated explicitly, and a new problem involving a different principle (odd or even number, high or low value, simple or double alternation) is presented. In two pilot studies, numbers of trials and errors to criterion correlated strongly with scores on WAIS Arithmetic., Digit Span, and Block Design for a randomly selected heterogeneous group of 10 testees and with course grades for 25 college students. This maze can be administered and scored by computer. Applications are many.