More On The Virtues Of VirtualBox – ACID (or AICD) Under Ubuntu 14.04 (By Way Of OpenSuse 11.2)

“Stop that!” – George Carlin

If you’ve obtained source code from an academic lab that was last developed some time ago and you spent a whole day installing libraries and symbolic links and redefining variables in your .bashrc and downgrading libraries and redefining paths and have 20 tabs open in your browser that all go to 20 different obscure error discussions on Stack Overflow and it’s late and you’re tired and you think you might not need the program after all if you do a bunch of other workaround things instead – what’s below is for you.

Academics have been developing small code for (nearly) millions of years to make their lives easier – and we all benefit when that code is made available to others (esp. when it helps in data analysis). When that code is a series of perl or python scripts, there’s generally little reason why you should have any run issues. When they call on external libraries or specific tools, generally that information is available in the README somewhere. Generally speaking, there’s no reason why a code shouldn’t work in a straightforward manner when the developer doesn’t make it known that something else needs be installed to make it work.

So, why doesn’t code A work on your linux box? A few possibilities.

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“OrtVc1 failed #1.” Workaround In Gaussian09; Warning About (Pre-)Resonance Raman Spectra In GaussView 4/5

And Happy New Year.

Two issues (one easily addressable, one only by external workaround) related to the prediction of Raman intensities in Gaussian09 – for which there’s next-to-nothing online to address either of them (likely because they don’t come up that often).

OrtVc1 failed #1.

In simulating the Raman spectra of very long (> C60) polyenes as a continuance of work related to the infinite polyacetylene case (see this post for details: Bond Alternation In Infinite Periodic Polyacetylene: Dynamical Treatment Of The Anharmonic Potential), I reached a length and basis set for which Gaussian provides the following output and error:

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Commensurate Urea Inclusion Crystals With The Guest (E,E)‐1,4-Diiodo-1,3-Butadiene

Published in Crystal Growth & Design (Cryst. Growth Des., 2013, 13 (9), pp. 3852–3855) earlier this year. The theory work is less impressive than the successful crystal growth, with initial solid-state efforts in Crystal09 only very recently now producing good results (leaving the molecular calculations to Gaussian09 in this paper). The procedure leading to the observed crystal structure of this inclusion complex is a significant step in the direction of testing the theory proposed in Bond Alternation In Infinite Periodic Polyacetylene: Dynamical Treatment Of The Anharmonic Potential published earlier this year in J. Mol. Struct.

2013dec20_DIBD_UIC

Caption: Two views along the ba and ca crystal axes of the (E,E)‐1,4-Diiodo-1,3-Butadiene : Urea Inclusion Complex.

Amanda F. Lashua, Tiffany M. Smith, Hegui Hu, Lihui Wei, Damian G. Allis, Michael B. Sponsler, and Bruce S. Hudson

Abstract: The urea inclusion compound (UIC) with (E,E)-1,4-diiodo-1,3-butadiene (DIBD) as a guest (DIBD:UIC) has been prepared and crystallographically characterized at 90 and 298 K as a rare example of a commensurate, fully ordered UIC. The crystal shows nearly hexagonal channels in the monoclinic space group P21/n. The DIBD guest molecules are arranged end-to-end with the nonbonding iodine atoms in the van der Waals contact. The guest structure is compared with that for DIBD at 90 K and with computations for the periodic UIC and isolated DIBD molecule.

Bond Alternation In Infinite Periodic Polyacetylene: Dynamical Treatment Of The Anharmonic Potential

In press (DOI:10.1016/j.molstruc.2012.07.051) in the Journal Of Molecular Structure. May go down in history as a hardest-fought paper acceptance. In a similar line of research as the [18]-annulene study, but exploring the infinite limit of geometry and bond length alternation energy barrier for this infinite case. If the numbers are correct, the infinite polyene chains (polyacetylene) do not exhibit bond length alternation because the Peierls’ barrier between the single-double and double-single bond alternate minima is below the vibrational zero-point level. Plenty of ramifications.

Bruce S. Hudson and Damian G. Allis

Abstract. The potential energy of the infinite periodic chain model of polyacetylene (pPA) is symmetric with two equivalent minima separated by the Peierls’ stabilization barrier. In this work it is shown how an energy scale and vibrational energy levels for this highly anharmonic Peierls’ degree of freedom can be estimated. Attention is given to the potential energy increase for large deformations. The Born-Kármán treatment of translational symmetry is applied. Two empirical methods and a direct periodic boundary condition (PBC) density functional theory (DFT) calculations are in semi-quantitative agreement, each leading to the conclusion that pPA has a zero-point level that is above the Peierls’ barrier. The argument does not depend critically on the barrier height or the other parameters of the model or the computation method. It is concluded that pPA will not exhibit bond alternation and that the zero-point average geometry does not preclude possible conductivity.

The Structure Of [18]-Annulene: Computed Raman Spectra, Zero-Point Level And Proton NMR Chemical Shifts

In press (DOI:10.1016/j.molstruc.2012.05.016) in the Journal Of Molecular Structure (Volume 1023, 12 September 2012, Pages 212–215) in the special issue: MOLECULAR VIBRATIONS AND STRUCTURES: THEORY AND EXPERIMENT — A collection of papers dedicated to Professor Jaan Laane on the occasion of his 70th birthday.

This paper on the “actual” geometry of [18]-annulene is part of several larger stories addressing a larger polyene (or larger-polyene) issue. First among these is the meaning of experimental results obtained by various spectroscopic methods (in this case, using previous X-ray, Raman (with the C2 (blue) and D6h (red) simulated spectra shown in the image above), IR, and NMR data that produce different results within the limitations of the methods to study the single molecule). Second is the quality of the theoretical method for reproducing certain types of spectroscopic data. In the case of the [N]-annulene series, the ever-present B3LYP density functional is found to produce the time-average geometry of [18]-annulene found in X-ray data, but another density functional (in this case, KMLYP), finds that bond-alternate minima exist. Third is the importance of the zero-point level in the treatment of systems for which bond-alternate geometries exist with transition-state barriers calculated to be below the zero-point level in the classical approximation of nuclear positions (the Born-Oppenheimer Approximation).

NOTE 1: The KMYLP density functional is called in Gaussian with the following keyword set:

BLYP iop(3/76=1000005570) iop(3/77=0000004430) iop(3/78=0448010000)

NOTE 2: Optimization and Frequency calculations must be performed as TWO SEPARATE CALCULATIONS. The iop-called density functional does not carry itself over between opt + freq (or other properties) in the same input file. If you opt + freq in the same input file, you will Opt with KMLYP but freq with BLYP. This will be obvious by the number of imaginary modes.

Bruce S. Hudson and Damian G. Allis

Abstract. [18]-annulene has been of great interest from the structural point of view of its bond alternation. High-level calculations based on structures selected for agreement with NMR spectra lead to a bond-alternate C2 form over a non-alternating planar D6h structure deduced from diffraction, infrared (IR) and electronic spectral studies. Here it is shown that computed Raman spectra for the D6h and C2 forms are expected to be very different. However, two equivalent non-D6h bond-alternate minima of D3h or C2 geometries are separated by only a small barrier along a motion that involves CC stretching and compression. It is shown here that the zero-point level is above the barrier for this species. In light of that fact, the NMR calculations are reconsidered with inclusion of zero-point level averaging.

Abinit 6.8.1 In Parallel With OpenMPI 1.4.1 In Ubuntu 10.04.2 LTS (And Related)

It has been a banner week for Ubuntu installations.

The installation of Abinit 5.6.5 with OpenMPI 1.3.1 (previously reported at www.somewhereville.com/?p=384) wasn’t bad, but several games had to be played (at the time) to make everything compile and run correctly. I’m pleased to report that Abinit 6.8.1 and OpenMPI 1.4.1 seem to play better together, this simplified considerably over the previous installation guide by the use of the apt-get version of OpenMPI 1.4.1. A bit of option calling in the configure step is needed (and the errors for not doing it are included below).

0. For the Antsy Copy+Paste Crowd

Commands below.

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The Terahertz Spectrum And Quantum Chemical Assignment Of 2,2,-Bithiophene In Cyclohexane

In press, in the journal Vibrational Spectroscopy. In a bit of a departure from the last several terahertz (THz) papers, this study involves the simulation of the solution-phase THz spectrum of the very, very thoroughly studied 2,2-bithiophene in solution (cis and trans geometries and lowest-frequency vibrational modes are provided in the figure below), a phase both easier and more difficult than the solid-state density functional theory (DFT) calculations that have been the mainstay of previous studies. Simplicity comes from the molecular symmetry and smaller size of the system under study, with no issues of the temperature dependence of the lattice constants or the intermolecular interaction predictions complicating the spectral assignment of the lowest frequency modes. The difficulty comes from the ability to employ multiple theoretical models to study the system and the need for far higher levels of theory in the gas phase to perform an analysis worthy of experimental comparison.

In this study, the DFT and MP2 quantum chemical calculations were used to consider molecular geometry, cis and trans conformational energy differences, rotational barrier heights, the prediction of normal mode energies, and relative peak intensities.

One topic addressed in solution that is not an issue in the crystals studied to date are the accessibility of relative conformational minima at ambient conditions (kT, room temperature). In the case of 2,2-bithiophene, the conformational flexibility is around the exocyclic thiophene-thiophene bond. With the description of the potential energy surface (PES) for rotation about the exocyclic bond determined by conformational calculations, the second step is the determination of relative populations of the cis and trans forms as a function of temperature. In this case, weighting of the PES by the Boltzmann distribution function yields the plot shown in the bottom of the figure below, from which the relative cis and trans populations can be determined by integration of the 0 to 90 (cis) and 90 to 180 (trans) regions.

The long-short of this particular study, which I save for the article itself, is that no single theory provides all the best answers, but sufficiently high levels of theory all do settle into the reasonable vicinity of accurate. At least, to the extent that all of the experimental data is in agreement.

Anna M. Fedor1, Damian G. Allis1,2, and Timothy M. Korter1

1. Department of Chemistry, Syracuse University, Syracuse, NY 13244 USA

2. Nanorex, Inc. Bloomfield Hills, MI 48302-7188 USA

Abstract: The room temperature solution-phase terahertz (THz, 7 to 165 cm-1) spectrum of 2,2-bithiophene in cyclohexane is reported. Density functional theory (B3LYP) and ab initio (MP2) methods employing the 6-311++G(2d,2p) and aug-cc-pVDZ basis sets are used to assign the THz vibrational structure and determine the relative populations of the cis and trans conformations, as well as the trans-trans rotational barrier height and the effects of the cyclohexane solvent on the predicted molecular geometries and vibrational frequencies. Significant differences are seen in the performance of the different theoretical methods, with the best performing method dependent upon the molecular property of interest. The best fit model of the experimental THz spectrum is achieved using MP2/aug-cc-pVDZ, which places the relative trans and cis populations at 54% and 46%, respectively.

www.elsevier.com/wps/find/journaldescription.cws_home/504273/description#description
en.wikipedia.org/wiki/Terahertz
en.wikipedia.org/wiki/Thiophene
en.wikipedia.org/wiki/Density_functional_theory
en.wikipedia.org/wiki/M%C3%B8ller-Plesset_perturbation_theory
en.wikipedia.org/wiki/KT_%28energy%29
en.wikipedia.org/wiki/Boltzmann_distribution
chemistry.syr.edu
www.nanorex.com

Gaussian98/03 Nonlinear Optical (NLO) Response Format Demystified (circa 2002)

If you’re looking for simple tricks to make your use of Gaussian98/03 all the easier, I highly recommend heading over to check on the state of Wawrzyniec Niewodniczański’s site, larryn.blogspot.com, who’s also begun compiling cheat sheets blog-style (which is what I’ve been trying to do with my site, as it’s tough enough to find timely advice and even harder to fumble through online help for a lot of the commercial quantum chemical programs). Wawrzek reminded me that there was at least one semi-useful page from my old site that I forgot to post in the transition to this current site, so here it is (I’ve not calculated a first hyperpolarizability in four years, but I assume nothing’s changed about the formatting).

Lower Triangular Format

“Lower triangular format” is the means by which Gaussian outputs the components of the 2nd Rank Tensor that is the molecular polarizability. Polarizability is, itself, simply the constant (mostly) by which the induced dipole moment of a molecule is related to the external electric field that is providing the perturbative “nudge” on the electron density. In short, this relationship looks like the following.

gaussian NLO equation

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