Frequently Asked Questions (FAQ)
[Data for Academic Use]
[Literature Data Missing in the DDB?]
[Empty Data Sets in the DDB]
[Predict Pure Group Fragmentation]
[MD5 File Verification]
[How to Cite the Dortmund Data Bank]
How can I access DDB data as a researcher at an academic institution?
- The educational version contains all data for the 30 common compounds and their mixtures.
- If you are interested in data for a certain compound or mixture, look at our online search.
- If you are interested in all data or a large subset of the data for one or more properties (VLE, LLE, …), licensing a database is a good option. Subset prices (e.g. all alcohol-alkane data) can be calculated upon request.)
In addition to the data licensed by my company or the few demo data it is possible to display empty sets (checkbox in the top of the data set table in the DDB Query result dialog). What is this about?
- In addition to the licensed and demo data (in the Explorer version only demo data) your installation contains a complete directory of all DDB data sets. Data sets not available in your license are "empty". You can request these data from email@example.com or preferably via our online search.
I checked for certain data and found out that data from a reference are not stored in the DDB
- We at DDBST try to cover the data available in the open literature to the highest possible completeness. Stored data come from open literature and other sources and only experimental data from the original reference are considered. Data from confidential reports and own measurements are usuall available only via the DDB.
If you are aware of data missing in the DDB we would gratefully appreciate any information that would help us to also include these measurements. If you should have data from sources like MSc. or PhD. theses or the like we would be happy to have a copy available so that we can enter also this data.
Why are group fragmentations not consistent with e.g. groups used in the Aspen-simulator?
- Aspen Tech is using a different fragmentation algorithm that may produce undesirable results in some special cases. In addition, some groups are defined in a more strict way in Predict Pure leading to different results.
Where are the group definitions for the different methods stored?
- Usually these definitions are stored in files with the extension ink. In a typical installation, most of these files are integrated into the code and therefore are not on the DDB-directory. If a file like e.g. UNIFAC.ink is stored on the DDB-directory, it is used instead of the UNIFAC.ink that is integrated into the code. This is for example important for the Consortium members, who have a special consortium UNIFAC.ink, UNIFACDO.ink , … on their DDB-directory.
Why does the entrainer selection program find no suitable entrainer for the system acetic acid/water.
- The entrainer selection software would usually find a list of entrainers. If you entered a low temperature for the separation (e.g. T=323 K), the pure component vapor pressures of acetic acid and water are 8.4 kPa resp. 13.5 kPa. These values together with the other limiting condition that the "Minimum Vapor Pressure Difference Entrainer - Binary Mixture" must be -10 kPa leads to the effect that no component can meet this criterion (would be Psat<(8.4-10) kPa, a negative value). Suitable entrainers can therefore only be found if you increase the temperature to a higher value where the lower saturated vapor pressure of the both components exceed this 10 kPa barrier or lower the value of the minimum vapor pressure difference. If you choose e. g. T=350 K some entrainers will be found.
Where are the sigma-profles for the calculation stored and how do I add profiles from my own quantum chemical calculations?
- The sigma profiles are usually stored under a special directory under your public DDB. In order to use your own calculation results the .cosmo file first has to be averaged.
How do I set a different directory for the sigma profiles?
- In the private DDB directory (start "DDB Configuration" from the jumpstart menu to identify it's location) there may be a text file called "ddbsp.ini". If it does not exist, create a textfile with this name. Add the following two lines to this file:
path=< path to .cosmo directory>
The path must end with the character "".
The directory must include the subdirectories "cosmo-rs(ol)" and "cosmo-sac" with the averaged profiles.
MD5 (short for Message-Digest 5) is a commonly used cryptographic technique for verifying the integrity of files and DDBST uses the MD5 hash code mainly for checking files from our download server.
The MD5 algorithm produces a hexadecimal number with 32 digits (=128 Bit) which is unique for the checked file. This number is normally called hash code. This hash code allows identifying changes to a file done by viruses or trojan horses or other malware because the MD5 numbers changes completely even for small changes.
There are many software tools for creating MD5 hashes - Microsoft does not distribute a tool with Windows but provides a program "fciv.exe" for download from its web pages, see http://support.microsoft.com/kb/841290.
A description of the MD5 algorithm is also available in the Wikipedia.
"Dortmund Data Bank, YYYY, www.ddbst.com"
to cite the Dortmund Databank. "YYYY" should be the version (the year) for the used data bank or the current year if data have been taken from the web site.