How Reliable Are Modern Density Functional Approximations to Simulate Vibrational Spectroscopies?

We show that properties of molecules with low-frequency modes calculated with density functional approximations (DFAs) suffer from spurious oscillations along the nuclear displacement coordinate due to numerical integration errors. Occasionally, the problem can be alleviated using extensive integration grids that compromise the favorable cost-accuracy ratio of DFAs. Since spurious oscillations are difficult to predict or identify, DFAs are exposed to severe performance errors in IR and Raman intensities and frequencies or vibrational contributions to any molecular property. Using Fourier spectral analysis and digital signal processing techniques, we identify and quantify the error due to these oscillations for 45 widely used DFAs. LC-BLYP and BH&H are revealed as the only functionals showing robustness against the spurious oscillations of various energy, dipole moment, and polarizability derivatives with respect to a nuclear displacement coordinate. Given the ubiquitous nature of molecules with low-frequency modes, we warrant caution in using modern DFAs to simulate vibrational spectroscopies.This paper is dedicated to Gernot Frenking on occasion of his 75th birthday. Grants PGC2018-098212-B-C21, PGC2018- 098212-B-C22, and IJCI-2017-34658 funded by MCIN/AEI/ 10.13039/501100011033 and “FEDER Una manera de hacer Europa”, and the grants funded by Diputación Foral de Gipuzkoa (Grant 2019-CIEN-000092-01), and Gobierno Vasco (Grants IT1254-19, PRE_2020_2_0015, and PIBA19- 0004) are acknowledged. R.Z. gratefully acknowledges support from the Polish National Science Center (Grant 2018/30/E/ ST4/00457)

Role of dispersion interactions in Endohedral TM@(ZnS)12 structures

Role of dispersion interactions in Endohedral TM@(ZnS)(12) structures[EN] II−VI semiconducting materials are gaining attention due to their optoelectronic properties. Moreover, the addition of transition metals, TMs, might give them magnetic properties. The location and distance of the TM are crucial in determining such magnetic properties. In this work, we focus on small hollow (ZnS)12 nanoclusters doped with TMs. Because (ZnS)12 is a cage-like spheroid, the cavity inside the structure allows for the design of endohedral compounds resembling those of C60. Previous studies theoretically predicted that the first-row TM(ZnS)12 endohedral compounds were thermodynamically unstable compared to the surface compounds, where the TM atom is located at the surface of the cluster. The transition states connecting both structure families were calculated, and the estimated lifetimes of these compounds were predicted to be markedly small. However, in such works dispersion effects were not taken into account. Here, in order to check for the influence of dispersion on the possible stabilization of the desired TM(ZnS)12 endohedrally doped clusters, several functionals are tested and compare to MP2. It is found that the dispersion effects play a very important role in determining the location of the metals, especially in those TMs with the 4s3d shell half-filled or completely filled. In addition, a complete family of TM doped (ZnS)12 nanoclusters is explored using ab initio molecular dynamics simulations and local minima optimizations that could guide the experimental synthesis of such compounds. From the magnetic point of view, the Cr(7S)@(ZnS)12 compound is the most interesting case, since the endohedral isomer is predicted to be the global minimum. Moreover, molecular dynamics simulations show that when the Cr atom is located at the surface of the cluster, it spontaneously migrates toward the center of the cavity at room temperature.Financial support comes from Eusko Jaurlaritza through project IT1254-19. The authors are thankful for technical and human support provided by SGIker (UPV/EHU, ERDF, EU). E.J.I. acknowledges the support of the Ikerbasque Fellowship. E.R.C. acknowledges funding from the Juan de la Cierva program IJCI-2017-34658

Actas del V Congreso ISUF-H Costa Rica 2021: Ciudades espontáneas versus ciudades planificadas: distintos retos, distintas realidades

En el año 2021 celebramos en Costa Rica la V edición del Congreso ISUF-H, los días 1, 2 y 3 de diciembre, con la Escuela de Arquitectura de la Universidad de Costa Rica como anfitriona del evento. El congreso “Ciudades espontáneas versus ciudades planificadas: distintos retos, distintas realidades” propuso como eje central una reflexión crítica sobre los procesos de urbanización planificada y urbanización espontánea, en el cual se fomente un abordaje de las ciudades como expresión de organización social, económica, ambiental y cultural, enfatizando el carácter ideológico de la urbanización y subrayando su continua construcción como resultado de construcciones complejas. La celebración de un nuevo congreso en América Latina, permitió reforzar la tradición crítica en el abordaje de las ciudades, y reforzar también la necesidad de plantear una perspectiva latinoamericana de los estudios urbanos, y por consiguiente de una teoría urbana latinoamericana. En esta ocasión el congreso se centró en ahondar en la temática de la forma urbana, desde perspectivas transversales que involucren las amplias disciplinas que asumen como objeto de discusión las problemáticas de la ciudad contemporánea y cuestionan la dicotomía planteada entre lo espontáneo y lo planificado. Para la Escuela de Arquitectura de la Universidad de Costa Rica y su Laboratorio de Ciudad y Territorio es un honor haber podido llevar a cabo esta nueva edición del congreso de la Asociación ISUF-H como segunda sede en un país latinoamericano. Relevante para fortalecer la temática de la forma urbana en la región, reforzando alianzas y estableciendo nuevas redes que permitan compartir conocimientos a partir de las experiencias de esas diversidades urbanas. Auspiciar el debate en torno a la morfología urbana y las diferencias entre esas ciudades espontáneas y las planificadas, fue una oportunidad para reunir a expertos de las distintas latitudes hispánicas.UCR::Vicerrectoría de Docencia::Ingeniería::Facultad de Ingeniería::Escuela de Arquitectur