Illinois 601 15. USC M S . received 14th M a y 1970Ahtract. Starting from bare-ion pseudopotentials, net crystal potentials are evalutiied in direct space by (a) the usual linear screening technique and (b) the Thomas-Fermi method. For the metals considered (Na and AI), the potentials are quite similar, crossing outside the cores and never differing by more than 0.02 a.u. in the case of Na nor by more than 0.2 a.u. in the case of Al. The similarity of the results based on (a) and (b) suggest the use of the pseudopotential concept in conjunction with the rather general method (b) under conditions when (a) is questionable, that is whenever the zeroth order uniform electron gas solution is a poor physical approximation to the actual system under study (specific examples being molecules, insulating solids and interfaces).Methods (a) and (bj both yield shallower wells than those most often used as input information in band structure calculations and obtained by superposing atomic data.

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Resumen: La gramática colonial titulada Arte de Lengua Cacchí para Bien comun es una de las fuentes principales para los estudios diacrónicos de la lengua q'eqchi'. El ori gen, autor y fecha de creación de la obra se desconocen. Una de las copias que fue hecha en 1875 por Hermann Berendt, un antropólogo alemán, también contiene sus observaciones sobre los ejemplos ofrecidos en el texto que recopiló con ayuda de un hablante nativo de q'eqchi'. Así pues, esta copia no sólo representa el estado de la lengua tal como se hablaba en los tiempos cuando fue creado el original, sino que también proporciona datos de la lengua de la segunda mitad del siglo xIx. Conside rando además los datos del habla contemporánea, se reconstruye etapa por etapa la evolución de algunos fragmentos de la gramática q'eqchi' (pronombres, preposicio nes, sistema verbal, procesos sintácticos) a lo largo de aproximadamente 400 años.PalabRas clave: q'eqchi', lenguas mayas, gramáticas coloniales, descripción lingüística, lingüística histórica. abstRact:The colonial grammar titled Arte de Lengua Cacchí para Bien comun is one of the main sources for diachronic studies on the Q'eqchi' language. Its origin, author and date of creation are unknown. One of the copies was made in 1875 by Hermann Berendt, a German anthropologist, and also contains his observations on the examples provided in the text, which he made with the help of a native Q'eqchi' speaker. Therefore, this copy not only represents the state of the language spoken in the times when the manuscript was created, but also supplies information about the language of the second half of the xIx century. Considering as well the modern language data, the evolution of some fragments of the Q'eqchi' grammar (pronouns, prepositions, verbal system, syntactic processes) is reconstructed, stage by stage, during four hundred years approximately.