COSMO implementations

Schafer A, Klamt A, Sattel D, Lohrenz JCW, Eckert F (2000) Cosmo implementation in turbomole Extension of an efficient quantum chemical code towards liquid systems. Phys Chem Chem Phys 2 2187-2193. 

The first step of the COSMO implementation was the development of a cavity-construction scheme. Since I did not know about the PCM method at that time, which might be considered now as an inexcusable ignorance for a scientist working in that area, I developed an independent code for the cavity construction. Nevertheless, I started from the same idea,... 

M. Diedenhofen, H.J. Werner and A. Klamt, MOLPRO COSMO implementation in preparation. 

In Section 2.1 the theoretical concept of COSMO as a CSM is explained. In Section 2.2 the general technical strategy of the COSMO implementations is presented, while in Section 2.3 special details of the various implementations in force-field, semi-empirical, ab initio, and density functional codes are discussed. Section 2.4 gives a general outlook on future improvements and the potential of COSMO. 

Although not necessarily related to the central COSMO idea, the COSMO implementations have a special efficient way of cavity construction, which is illustrated schematically in Figure 1. The cavity is assumed to be a kind of SES. To construct this surface, in a first step the SAS is built as the exterior of all spheres of radius R, -F / soiv, where the / , are the radii of the atoms, usually defined as element specific radii, and Rsoiv is some radius representing a typical maximum curvature of solvent molecular surfaces.The default for Rsoiv is set to 1 A, and this has turned out to be a good choice for a great variety of solvents. R oiv should not be misinterpreted as a mean solvent radius, nor modified for different solvents. All spheres are... 

Different COSMO Implementations and Their Special Features... 

In this section we apply the theory developed above to some representative solvents, in order to demonstrate its potential to give a new qualitative insight into solvation phenomena. The underlying default parameters for the cavity construction. These a-profiles are shown in Figure 3, while Figure 4 presents the a-potentials according to equation (20). 

Smooth COSMO solvation model. We have recently extended our smooth COSMO solvation model with analytical gradients [71] to work with semiempirical QM and QM/MM methods within the CHARMM and MNDO programs [72, 73], The method is a considerably more stable implementation of the conventional COSMO method for geometry optimizations, transition state searches and potential energy surfaces [72], The method was applied to study dissociative phosphoryl transfer reactions [40], and native and thio-substituted transphosphorylation reactions [73] and compared with density-functional and hybrid QM/MM calculation results. The smooth COSMO method can be formulated as a linear-scaling Green s function approach [72] and was applied to ascertain the contribution of phosphate-phosphate repulsions in linear and bent-form DNA models based on the crystallographic structure of a full turn of DNA in a nucleosome core particle [74],... 

These immediate and simple findings motivated me to accept Gerrit Schuiirmann s request and to implement COSMO as a new kind of SCRF model in the semi-empirical quantum chemistry package MOPAC [39]. Shortly afterwards, I met Jimmy Stewart, the author of the MOPAC package, in a European Computational Chemistry Workshop in Oxford, where he was available as a supervisor for a entire workshop. I gave a short presentation of my COSMO ideas and he was interested to get COSMO as the first solvation model in MOPAC. Therefore, he introduced me to some extend to the MOPAC program code, and we identified the places where COSMO would have to link in. 

We have now achieved a situation in which dielectric continuum solvation models in general, and especially COSMO, are quite well established for SCF ground-state calculations of organic molecules. Many of the methods, tools, and properties available for gas-phase calculation can also be performed in a dielectric continuum solvation model. The PCM model including C-PCM provides the greatest breadth of implemented functionality. 

These considerable solvent-dependent shifts demonstrate that for molecules with such pronounced conformational ambiguity, the equilibration of conformations has to be taken into account in the calculation of thermodynamic phase-equilibrium data. In order to enable a consistent treatment, we have implemented an automated conformation equilibration scheme in COSMO therm. A compound X can be represented by a set of COSMO-files for the conformers, and a multiplicity ojx(i) can be assigned to each con-former based on geometrical degeneration aspects. Then the population of a conformer, i, in a solvent S is calculated as... 

This procedure of COSMO-RS solvent screening, meanwhile, is applied routinely in a number of large chemical companies. One successful COSMO-RS-based solvent replacement has been reported. This is already implemented in an industrial process and saves more than a million Euro per year [102]. Owing to the secrecy restrictions of most industrial projects, it is likely that other successful applications exist, but are unpublished. 

Technically, the AM1/DFT correction is now implemented as a combination of the structure analysis tool COSMO/yze developed for COSMO/rag and the MOPAC2002 program [59]. COSMO/y-ze analyses the bond types of a new protein and writes an input file for MOPAC, which contains all the correction charges for atoms and bond centers. By a small modification, MOPAC2002 is now able to read these AM1/DFT correction charges and to add the corresponding corrections to the electrostatic potential on the COSMO surface at the end of a MOPAC/COSMO calculation. In a final COSMO call, the improved potential is converted into updated COSMO charges and a COSMO file with quality closer to BP-SVP quality is written. 

C3 K. Baldridge and A. Klamt, GAMESS/COSMO First principle implementation of solvent effects without outlying charge error, J. Chem. Phys., 106 (1997) 6622-6633. 

A. Bliznyuk, Linear-scaling COSMO, as implemented in Mopac 2002 [59]. 

Despite the simple form of Equation (1.83), the detailed formulation of an extended Lagrangian for CPCM is not a straightforward matter and its implementation remains challenging from the technical point of view. Nevertheless, is has been attempted with some success by Senn and co-workers [31] for the COSMO-ASC model in the framework of the Car-Parrinello ab initio MD method. They were able to ensure the continuity of the cavity discretization with respect to the atomic positions, but they stopped short of providing a truly continuous description of the polarization surface charge as suggested,... 

The conductor-like screening model (COSMO) approach replaces the dielectric medium with a conducting medium (basically a medium that effectively has an infinite dielectric constant). Interlocking spheres are used to generate the cavity. The conductor-like screening has been implemented as a PCM version, called CPCM.128,129... 

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