The fluid inclusions in mantle rocks and melt indicated that a large amount of CO₂ fluid exists in the deep earth, which is of great significance for understanding the deep carbon cycle and the composition of mantle. However, it was also suggested that carbonate minerals were likely to be the main host of mantle carbon. At the same time, the distribution and behavior of carbon in the mantle still remain a puzzle. In this paper, the adsorption behavior and occurrence characteristics of supercritical CO₂ in magnesite (MgCO₃) pores were studied by the Grand Canonical Monte Carlo method (GCMC) under the different conditions of CO₂ pressures (0–100 MPa), temperatures (350–1500 K) and the pore sizes (7.5–30 Å). The simulated results showed that the adsorption of CO₂ in magnesite was a physical adsorption, which was mainly controlled by the intermolecular force. The gas adsorption became more stable when the adsorption site shifted from the high energy site to the low energy site with increasing pressure (P) and decreasing temperature (T) and pore size. At the same time, the variations of excess adsorption amounts of CO₂ in the pores of magnesite (N_excess) under the different conditions were quantitatively calculated. It was found that the N_excess decreased with increasing T, but increased with increasing P and pore size. The results favor understanding the CO₂ migration, seismic precursor observations, and heat transfer process in the deep earth.

地幔岩石和熔体中的流体包裹体表明，深层土壤中存在大量的CO ₂流体，这对于理解深部碳循环和地幔组成具有重要意义。但是，也有人认为碳酸盐矿物可能是地幔碳的主要来源。同时，地幔中碳的分布和行为仍然是一个难题。本文采用大正则蒙特卡罗方法（GCMC）研究了在不同CO ₂条件下菱镁矿（MgCO ₃）中超临界CO ₂的吸附行为和发生特征。压力（0–100 MPa），温度（350–1500 K）和孔径（7.5–30Å）。模拟结果表明，菱镁矿中CO ₂的吸附为物理吸附，主要受分子间力控制。当压力（P）增加，温度（T）和孔径减小时，吸附位置从高能位置转移到低能位置时，气体吸附变得更加稳定。同时，定量计算了不同条件下菱镁矿孔内CO ₂过量吸附量的变化（N_过量）。发现氮的_过量随着T的增加而减少，但是随着P和孔径的增加而增加。结果有助于理解CO₂地下深处的迁移，地震前兆观测和传热过程。