菱镁矿MgCO_3热力学性质的第一性原理研究

Research of the Thermodynamic Properties on the Magnesite by First Principles

采用第一性原理(First principles)的赝势平面波法,结合广义梯度近似(GGA)及PW91算法,对煤中含镁物质菱镁矿MgCO3的电子结构和热力学性质进行了计算。首先,对菱镁矿MgCO3的结构进行优化,使其达到最稳定的状态,计算结果表明菱镁矿MgCO3晶胞体积V0=289.5320a.u.3,晶胞参数为a=b=4.7888,c=14.5785。其次,由声子谱态密度方法计算了菱镁矿MgCO3的熵、热容、焓及吉布斯自由能。最后,由相应的数据作出图像,再由图像拟合成函数表达式。由微观计算得出的结果为煤灰结渣问题的研究提供了理论上的指导。

Using the pseudo potential plane-wave method based on the first principles, combining the gener〉 lized gradient approximation（GGA） and PW91 algorithms, the structural and thermodynamic properties of the magne site MgCO3 in the coal were calculated. Firstly, the structure of magnesite MgCO3 and enabled it to achieve the most stable state were optimized. The calculated results indicate the volume VO and lattice parameter of the unit cell are 289. 5320a. u. 3, and a=b= 4. 7888A, c= 14. 5785,A respectively. Secondly, the entropy, heat capacity, enthalpy, Gibbs free energy of the magnesite MgCO3 by the phonon spectra state density are calculated. At last, the images ac cording to the data are made and the curves into the function expression are fitted. So, the micro calculation provided the theoretical guidance about the coal ash slag-bonding problems.