TY - JOUR
T1 - An electrostatic correction for improved crystal density predictions of energetic ionic compounds
AU - Politzer, Peter
AU - Martinez, Jorge
AU - Murray, Jane S.
AU - Concha, Monica C.
N1 - Funding Information:
We thank a reviewer of our earlier article dealing with molecular crystal densities who suggested the present work, and Dr Michael Göbel and Dr Felipe A. Bulat for useful discussions. PP, JSM and MCC appreciate the support of the Defense Threat Reduction Agency, Contract No. HDTRA1-07-1-0002, Project Officer Dr William Wilson. JM acknowledges the financial support from Program B: HPC & Materials SEPARI Centro TIC, FONDEF project CTICV002.
PY - 2010/1
Y1 - 2010/1
N2 - In recent years, there has been considerable interest in predicting the crystal densities of both molecular and ionic energetic compounds using the computed volumes Vm of the isolated gas phase molecules or ions. The surfaces enclosing the volumes are taken to be the 0.001 au (electrons/bohr3) contours of the molecules' and ions' electronic densities. For molecular solids, it is known that the ratio M/Vm (M = molecular mass) gives densities that are overall reasonably good, although they can be markedly improved by introduction of an electrostatic interaction correction term. For ionic solids, the subject of this paper, the ratio M/Vm (M = formula unit mass) is not nearly as effective; Vm tends to be significantly larger than the effective volumes of the ions in the crystal, leading to underestimated densities, with an average absolute error of 0.089 g/cm3. The correction term that improves molecular crystal densities is not applicable in the case of ionic solids; however we show, for a database of 25 compounds plus five test cases, that an average absolute error of 0.033 g/cm3 can be achieved by combining M/Vm with terms involving the average positive and negative potentials and areas on the cationic and anionic surfaces. The root-mean-square error is 0.040 g/cm3.
AB - In recent years, there has been considerable interest in predicting the crystal densities of both molecular and ionic energetic compounds using the computed volumes Vm of the isolated gas phase molecules or ions. The surfaces enclosing the volumes are taken to be the 0.001 au (electrons/bohr3) contours of the molecules' and ions' electronic densities. For molecular solids, it is known that the ratio M/Vm (M = molecular mass) gives densities that are overall reasonably good, although they can be markedly improved by introduction of an electrostatic interaction correction term. For ionic solids, the subject of this paper, the ratio M/Vm (M = formula unit mass) is not nearly as effective; Vm tends to be significantly larger than the effective volumes of the ions in the crystal, leading to underestimated densities, with an average absolute error of 0.089 g/cm3. The correction term that improves molecular crystal densities is not applicable in the case of ionic solids; however we show, for a database of 25 compounds plus five test cases, that an average absolute error of 0.033 g/cm3 can be achieved by combining M/Vm with terms involving the average positive and negative potentials and areas on the cationic and anionic surfaces. The root-mean-square error is 0.040 g/cm3.
KW - Electrostatic potentials
KW - Ionic crystal density
KW - Ionic energetic compounds
KW - Ionic volumes/surface areas
UR - http://www.scopus.com/inward/record.url?scp=77953525088&partnerID=8YFLogxK
U2 - 10.1080/00268971003702221
DO - 10.1080/00268971003702221
M3 - Article
AN - SCOPUS:77953525088
SN - 0026-8976
VL - 108
SP - 1391
EP - 1396
JO - Molecular Physics
JF - Molecular Physics
IS - 10
ER -